One day this fall, I watched an electronic sign outside the Broadway-Lafayette subway station in Manhattan switch seamlessly between an ad for makeup and one promoting the website Pickyourbaby.com, which promises a way for potential parents to use genetic tests to influence their baby’s traits, including eye color, hair color, and IQ.

Inside the station, every surface was wrapped with more ads—babies on turnstiles, on staircases, on banners overhead. “Think about it. Makeup and then genetic optimization,” exulted Kian Sadeghi, the 26-year-old founder of Nucleus Genomics, the startup running the ads. To his mind, one should be as accessible as the other. 

Nucleus is a young, attention-seeking genetic software company that says it can analyze genetic tests on IVF embryos to score them for 2,000 traits and disease risks, letting parents pick some and reject others. This is possible because of how our DNA shapes us, sometimes powerfully. As one of the subway banners reminded the New York riders: “Height is 80% genetic.”

The day after the campaign launched, Sadeghi and I had briefly sparred online. He’d been on X showing off a phone app where parents can click through traits like eye color and hair color. I snapped back that all this sounded a lot like Uber Eats—another crappy, frictionless future invented by entrepreneurs, but this time you’d click for a baby.

I agreed to meet Sadeghi that night in the station under a banner that read, “IQ is 50% genetic.” He appeared in a puffer jacket and told me the campaign would soon spread to 1,000 train cars. Not long ago, this was a secretive technology to whisper about at Silicon Valley dinner parties. But now? “Look at the stairs. The entire subway is genetic optimization. We’re bringing it mainstream,” he said. “I mean, like, we are normalizing it, right?”

Normalizing what, exactly? The ability to choose embryos on the basis of predicted traits could lead to healthier people. But the traits mentioned in the subway—height and IQ—focus the public’s mind toward cosmetic choices and even naked discrimination. “I think people are going to read this and start realizing: Wow, it is now an option that I can pick. I can have a taller, smarter, healthier baby,” says Sadeghi.

Nucleus got its seed funding from Founders Fund, an investment firm known for its love of contrarian bets. And embryo scoring fits right in—it’s an unpopular concept, and professional groups say the genetic predictions aren’t reliable. So far, leading IVF clinics still refuse to offer these tests. Doctors worry, among other things, that they’ll create unrealistic parental expectations. What if little Johnny doesn’t do as well on the SAT as his embryo score predicted?

The ad blitz is a way to end-run such gatekeepers: If a clinic won’t agree to order the test, would-be parents can take their business elsewhere. Another embryo testing company, Orchid, notes that high consumer demand emboldened Uber’s early incursions into regulated taxi markets. “Doctors are essentially being shoved in the direction of using it, not because they want to, but because they will lose patients if they don’t,” Orchid founder Noor Siddiqui said during an online event this past August.

Sadeghi prefers to compare his startup to Airbnb. He hopes it can link customers to clinics, becoming a digital “funnel” offering a “better experience” for everyone. He notes that Nucleus ads don’t mention DNA or any details of how the scoring technique works. That’s not the point. In advertising, you sell the sizzle, not the steak. And in Nucleus’s ad copy, what sizzles is height, smarts, and light-colored eyes.

It makes you wonder if the ads should be permitted. Indeed, I learned from Sadeghi that the Metropolitan Transportation Authority had objected to parts of the campaign. The metro agency, for instance, did not let Nucleus run ads saying “Have a girl” and “Have a boy,” even though it’s very easy to identify the sex of an embryo using a genetic test. The reason was an MTA policy that forbids using government-owned infrastructure to promote “invidious discrimination” against protected classes, which include race, religion and biological sex.

Since 2023, New York City has also included height and weight in its anti-discrimination law, the idea being to “root out bias” related to body size in housing and in public spaces. So I’m not sure why the MTA let Nucleus declare that height is 80% genetic. (The MTA advertising department didn’t respond to questions.) Perhaps it’s because the statement is a factual claim, not an explicit call to action. But we all know what to do: Pick the tall one and leave shorty in the IVF freezer, never to be born.

This article first appeared in The Checkup, MIT Technology Review’s weekly biotech newsletter. To receive it in your inbox every Thursday, and read articles like this first, sign up here.

A West Coast biotech entrepreneur says he’s secured $30 million to form a public-benefit company to study how to safely create genetically edited babies, marking the largest known investment into the taboo technology.  

The new company, called Preventive, is being formed to research so-called “heritable genome editing,” in which the DNA of embryos would be modified by correcting harmful mutations or installing beneficial genes. The goal would be to prevent disease.

Preventive was founded by the gene-editing scientist Lucas Harrington, who described his plans yesterday in a blog post announcing the venture. Preventive, he said, will not rush to try out the technique but instead will dedicate itself “to rigorously researching whether heritable genome editing can be done safely and responsibly.”

Creating genetically edited humans remains controversial, and the first scientist to do it, in China, was imprisoned for three years. The procedure remains illegal in many countries, including the US, and doubts surround its usefulness as a form of medicine.

Still, as gene-editing technology races forward, the temptation to shape the future of the species may prove irresistible, particularly to entrepreneurs keen to put their stamp on the human condition. In theory, even small genetic tweaks could create people who never get heart disease or Alzheimer’s, and who would pass those traits on to their own offspring.

According to Harrington, if the technique proves safe, it “could become one of the most important health technologies of our time.” He has estimated that editing an embryo would cost only about $5,000 and believes regulations could change in the future. 

Preventive is the third US startup this year to say it is pursuing technology to produce gene-edited babies. The first, Bootstrap Bio, based in California, is reportedly seeking seed funding and has an interest in enhancing intelligence. Another, Manhattan Genomics, is also in the formation stage but has not announced funding yet.

As of now, none of these companies have significant staff or facilities, and they largely lack any credibility among mainstream gene-editing scientists. Reached by email, Fyodor Urnov, an expert in gene editing at the University of California, Berkeley, where Harrington studied, said he believes such ventures should not move forward.

Urnov has been a pointed critic of the concept of heritable genome editing, calling it dangerous, misguided, and a distraction from the real benefits of gene editing to treat adults and children. 

In his email, Urnov said the launch of still another venture into the area made him want to “howl with pain.”  

Harrinton’s venture was incorporated in Delaware in May 2025,under the name Preventive Medicine PBC. As a public-benefit corporation, it is organized to put its public mission above profits. “If our research shows [heritable genome editing] cannot be done safely, that conclusion is equally valuable to the scientific community and society,” Harrington wrote in his post.

Harrington is a cofounder of Mammoth Biosciences, a gene-editing company pursuing drugs for adults, and remains a board member there.

In recent months, Preventive has sought endorsements from leading figures in genome editing, but according to its post, it had secured only one—from Paula Amato, a fertility doctor at Oregon Health Sciences University, who said she had agreed to act as an advisor to the company.

Amato is a member of a US team that has researched embryo editing in the country since 2017, and she has promoted the technology as a way to increase IVF success. That could be the case if editing could correct abnormal embryos, making more available for use in trying to create a pregnancy.

It remains unclear where Preventive’s funding is coming from. Harrington said the $30 million was gathered from “private funders who share our commitment to pursuing this research responsibly.” But he declined to identify those investors other than SciFounders, a venture firm he runs with his personal and business partner Matt Krisiloff, the CEO of the biotech company Conception, which aims to create human eggs from stem cells.

That’s yet another technology that could change reproduction, if it works. Krisiloff is listed as a member of Preventive’s founding team.

The idea of edited babies has received growing attention from figures in the cryptocurrency business. These include Brian Armstrong, the billionaire founder of Coinbase, who has held a series of off-the-record dinners to discuss the technology (which Harrington attended). Armstrong previously argued that the “time is right” for a startup venture in the area.

Will Harborne, a crypto entrepreneur and partner at LongGame Ventures, says he’s “thrilled” to see Preventive launch. If the technology proves safe, he argues, “widespread adoption is inevitable,” calling its use a “societal obligation.”

Harborne’s fund has invested in Herasight, a company that uses genetic tests to rank IVF embryos for future IQ and other traits. That’s another hotly debated technology, but one that has already reached the market, since such testing isn’t strictly regulated. Some have begun to use the term “human enhancement companies” to refer to such ventures.

What’s still lacking is evidence that leading gene-editing specialists support these ventures. Preventive was unsuccessful in establishing a collaboration with at least one key research group, and Urnov says he had harsh words for Manhattan Genomics when that company reached out to him about working together. “I encourage you to stop,” he wrote back. “You will cause zero good and formidable harm.”

Harrington thinks Preventive could change such attitudes, if it shows that it is serious about doing responsible research. “Most scientists I speak with either accept embryo editing as inevitable or are enthusiastic about the potential but hesitate to voice these opinions publicly,” he told MIT Technology Review earlier this year. “Part of being more public about this is to encourage others in the field to discuss this instead of ignoring it.”

The agents scrolling through his feeds would have learned that Hanna is part of Israel’s small Arab Christian minority, a nonbinary LGBTQ-rights advocate, and an outspoken critic of the Gaza occupation, who uses his social media accounts to post images of atrocities and hold up a mirror to scientific colleagues including those at the Weizmann Institute of Science, the pure-science powerhouse where he works—Israel’s version of Caltech or Rockefeller University. In his luggage, they would have found his keffiyeh, or traditional headscarf, which Hanna last year vowed to wear at lecture podiums on his many trips abroad.

Hanna had been stopped before; he knew the routine. Anything to declare? Any biological samples? But this time the agents’ questions touched on a specific new topic: embryos.

Weeks earlier, a Harvard University researcher had been arrested for having frog embryos in her luggage and sent to a detention center in Louisiana. Hanna didn’t have any specimens from his lab, but if he had, it would have been surprisingly hard to say what they were. That’s because his lab specializes in creating synthetic embryo models, structures that resemble real embryos but don’t involve sperm, eggs, or fertilization. 

Instead of relying on the same old recipe biology has followed for a billion years, give or take, Hanna is coaxing the beginnings of animal bodies directly from stem cells. Join these cells together in the right way, and they will spontaneously attempt to organize into an embryo—a feat that’s opening up the earliest phases of development to scientific scrutiny and may lead to a new source of tissue for transplant medicine.

Soon it could be difficult to distinguish between a real human embryo—the kind with legal protections—and one conjured from stem cells.

In 2022, working with mice, Hanna reported he’d used the technique to produce synthetic embryos with beating hearts and neural folds—growing them inside small jars connected to a gas mixer, a type of artificial womb. The next year, he repeated the trick using human cells. This time the structures were not so far developed, still spherical in shape. Nonetheless, they were incredibly realistic mimics of a two-week-old human embryo, including cells destined to form the placenta. 

These sorts of models aren’t yet the same as embryos. It’s rare that they form correctly—it takes a hundred tries to make one—and they skip past normal steps before popping into existence. Yet to scientists like the French biologist Denis Duboule, Hanna’s creations are “entirely astonishing and very disturbing.” Soon, Duboule expects, it could be difficult to distinguish between a real human embryo—the kind with legal protections—and one conjured from stem cells. 

Hanna is the vanguard of a wider movement that’s fusing advanced methods in genetics, stem-cell biology, and still-­primitive artificial wombs to create bodies where they’ve never grown before—outside the uterus. Joining the chase are researchers at Caltech, the University of Cambridge, and Rockefeller in New York, as well as a growing cadre of startup companies with commercial aims. There’s Renewal Bio, a startup Hanna cofounded, which hopes to grow synthetic embryos as a source of youthful replacement cells, such as bits of liver or even eggs. In Europe, Dawn Bio has started placing a type of embryo model called a blastoid on uterine tissue. That will light up a pregnancy test and could, the company thinks, provide new insights into IVF medicine. Patent offices in the US and Europe are seeing a flood of claims as universities grasp for exclusive commercial control over these new types of beings. 

Hanna declined a request to discuss his research for this story. But for the last three years, MIT Technology Review has followed Hanna across online presentations, lecture halls, and two in-person ethics meetings, both organized by the Global Observatory for Genome Editing, a public consultation project where he agreed to engage with religious scholars, bioethicists, and other experts. What emerged is a remarkable picture of a scientist working at a Nobel Prize level but whose research, though approved by his institution, raises serious long-term ethical questions.

Exactly how far Hanna has taken his models of the human embryo is an open question. According to public comments from Renewal Bio, the answer is at least 28 days. But it’s possibly further. One scientist in contact with the company said he thought they’d reached close to day 40, a point where you would see the beginning of eyes and budding limbs. Renewal did not respond to a request for comment.

But even if he hasn’t gotten that far yet, Hanna intends to. His team is “trying to make entities at more advanced stages—depending on the goal, it could be day 30 in development, day 40, or day 70,” he told an audience last May in Cambridge, Massachusetts, where he’d traveled to join a panel discussion involving religious scholars and social scientists at the Global Observatory’s annual summit. The more advanced versions would be similar in size and development to a fetus in the third month of pregnancy. 

O. Carter Snead, a bioethicist from the University of Notre Dame who led the panel featuring Hanna, approached me afterward to ask if I’d heard what the scientist had said. Snead was surprised that Hanna had so frankly disclosed his goals and that no one had objected, or maybe even grasped what it meant. Perhaps, Snead thinks, this technology won’t sink in until people can see it with their own eyes. “If you had one of these spinning bottles with something that looked like a human fetus inside it, I think you’d get people’s attention,” he says. “That’s going to be like, whoa—what are we doing?”

Snead, a Catholic who sits on a panel that advises the Vatican, also was not comforted by Hanna’s plan to make sure his models, if they advance to later stages of development, will pass ethical scrutiny. That plan involves blocking the formation of the head, brain, or perhaps heart of the synthetic structures, by means including genetic modification. If there’s no brain, Hanna’s reasoning goes, there’s no awareness, no person, and no foul. Just a clump of organs.

Snead says that’s not the same standard of humanity he knows, which treats all humans the same, regardless of their intellectual capacity or anything else. “What is considered human? Who is considered human?” wonders Snead. “It’s who’s in and who’s out. There is a dramatic consequence of being in versus out of the boundaries of humanity.”

The beginnings of bodies

Each of us—me, you the reader, and Jacob Hanna—started as a fertilized egg, a single cell that’s able to divide and dynamically carry out a program to build a complete body with all its organs and billions of specialized cells. Science has long sought ways to seize on that dramatic potential. A first step came in the 1990s, when scientists were able to isolate powerful stem cells from five-day-old embryos created through in vitro fertilization—and keep them growing in their labs. These embryonic stem cells had the inherent potential to become any other type of cell. If they could be directed in the lab to form, for example, neurons or the insulin-making cells that diabetics need, that would open up a way to treat disease using cell transplants. 

But these lab recipes are often unsuccessful, which explains the general lack of new stem-cell treatments. “The sad truth is that over 25 years that we’ve been working on this problem, there are about 10 cell types you make that have reasonable function,” says Chad Cowan, chief scientific officer of the stem-cell company Century Therapeutics. If we think of the body as a car, he explains, “we’ve got only spark plugs. We maybe have some tires.” The body’s most potent blood-forming cells in particular “never appear,” according to Cowan, even though biotech companies have spent millions trying to make them.

Hanna’s startup plans to use synthetic embryos as a kind of “bioprinter,” producing medically valuable cells in cases where other methods have failed.

It turns out, though, that stem cells retain a natural urge to work together. Scientists began to notice that, when left alone, the cells would join into blobs, tubes, and cavities—some of which resembled parts of an embryo. 

Early versions of these structures were crude, even just a swirling film of cells on a glass slide. But each year, they have grown more realistic. By 2023, Hanna was describing what he called a “bona fide” human embryo model that was “fully integrated,” with all the major parts arranged in an architecture that was hard to distinguish from the real thing. 

His company, Renewal, plans to use these synthetic embryos as a kind of “bioprinter,” producing medically valuable cells in cases where other methods have failed. This could be particularly valuable if the synthetic embryos are a perfect match with a patient’s DNA. And that’s possible too: These days reprogramming anyone’s skin cells into stem cells is easily done. Hanna has tried it on himself, transforming his own cells into synthetic embryos. 

Hanna’s research, and that of other groups, has at times collided with a powerful scientific body called the International Society for Stem Cell Research, or ISSCR, a self-governance organization that sets boundaries about what research can and can’t be published and what terminology to use. That’s to shield scientists from sensational headlines, public backlash, or the reach of actual regulators. 

The organization has taken a particularly categorical position on structures made from stem cells, saying they are mere “models.” According to a statement it fired off in 2023, “embryo models are neither synthetic nor embryos”—and, it added, they “cannot and will not develop to the equivalent of postnatal stage human.” 

Many scientists, including Hanna, agree no one should ever try to make a stem-cell baby. But he is fairly certain these structures will become more realistic and can grow further. In fact, that may be the real test of what an embryo is: whether it can dynamically keep reaching new stages of development, especially organogenesis, or the first emergence of organs. The language in the ISSCR statement, he complained, was “brainwashing.” 

Replacement parts

Most of the commercial projects involving synthetic embryos are doomed to a short and fitful life as the technology proves too difficult or undeveloped. But the idea isn’t going away. Instead, there are signals it’s getting bigger, and weirder. In an editorial published in March by MIT Technology Review, a group of Stanford scientists put forward a proposal for what they called “bodyoids,” arguing that stem cells and artificial wombs may lead to an “unlimited source” of nonsentient human bodies for use in drug research or as organ donors. One of its authors, Henry Greely, among the foremost bioethicists in the US, posted on Bluesky that even though the idea gives him “some creeps,” he added his name because he feels it is plausible enough to need discussion, and “soon.”

Especially in the Bay Area, headless bodies are having a moment. The Stanford biologist Hiro Nakauchi, another “bodyoids” author, said the editorial provided a surprise entrée for him into a world of stealth startups already pursuing synthetic embryos, artificial wombs, and body-part “replacement.” He met the CEO of Hanna’s company, signing on as an advisor. But other teams have still more radical plans. One venture capitalist introduced him to a longevity entrepreneur tinkering with a plan for head transplants. The idea: Swap your aged head onto the body of a younger clone. That company claims to have a facility on a Caribbean island “just like Jurassic Park,” Nakauchi says.   

These sorts of plans—real or rumored—have gotten the attention of the stem-cell police, the ISSCR. This June, an ethics committee led by Amander Clark, a fetal specialist at UCLA and a past president of the society, wrote that it had become aware of “commercial and other groups raising the possibility of building an embryo in vitro” and bringing it to viability inside “artificial systems.” Though the ISSCR had previously decreed that embryo models “cannot and will not” develop to term, it now declared efforts aiming at viability “unsafe and unethical,” placing them in a “prohibited” category. It added that the ban would cover “any purpose: reproductive, research, or commercial.” 

Blurred boundaries

Clark and her colleagues are right that, for the foreseeable future, no one is going to decant a full-term baby out of a bottle. That’s still science fiction. But there’s a pressing issue that needs to be dealt with right now. And that’s what to do about synthetic embryo models that develop just part of the way—say for a few weeks, or months, as Hanna proposes. 

Because right now, hardly any laws or policies apply to synthetic embryos. One reason is their unnatural origin: Because these entities don’t start with conception and grow in labs, most existing laws won’t cover them. That includes the Fetus Farming Prohibition Act, legislation passed unanimously in 2006 by the US Congress, which sought to prevent anyone from growing a fetus for its organs. But that law references “a human pregnancy” and a “uterus”—and there would be neither if a synthetic embryo were grown in a mechanical vessel. 

Another policy under pressure is the “14-day rule,” a widely employed convention that natural embryos should not be grown longer than two weeks in the lab. Though it’s a mostly arbitrary stopping point, it’s been convenient for laboratory scientists to know where their limit is. But that rule isn’t being applied to the embryo models. For instance, even though the United Kingdom has a 14-day rule enshrined in law, that legislation doesn’t define what an embryo is. To scientists working on models, that’s a critical loophole. If the structures aren’t considered true embryos, then the rule doesn’t apply.  

Last year, the University of Cambridge, in the UK, described the situation as a “grey area” and said it “has left scientists and research organisations uncertain about the acceptable boundaries of their work, both legally and ethically.” 

Researchers at the university, which is a hot spot for human embryo models, have been working with one that has advanced features, including beating heart cells. But the appearance of distinctive features under their microscopes is unsettling—even to scientists. “I was scared, honestly,” Jitesh Neupane, who led that work, told the Guardian in 2023. “I had to look down and look back again.” 

That particular stem-cell model isn’t complete—it entirely lacks placenta cells and a brain. So it’s not a real embryo. But it could get ever trickier to insist the models don’t count, given the accelerating race to make them more realistic. To Duboule, scientists are caught in a “fool’s paradox” and a “rather unstable situation.”

Even incomplete models raise the question of where to draw the line. Should you stop when it can feel pain? When it’s just too human-looking for comfort? Scientific leaders may soon have to decide if there are “morally significant” human features—like hands or a face—that should be avoided, whether the structure has a brain or not. “I personally think there should be regulation, and many in the field believe this too,” says Alejandro De Los Angeles, a stem-cell biologist affiliated with the University of Central Florida. 

“I always live in fear that I might find myself embroiled in some kind of a scandal … Things can shift very quickly for political reasons.”

Jacob Hanna

Hanna says he has all the necessary approvals in Israel to carry his work forward. But he also worries that the ground rules could change. “I’m almost the only one [in Israel] doing these kinds of experiments, and I always live in fear that I might find myself embroiled in some kind of a scandal,” he says. “Things can shift very quickly for political reasons.” 

And his statements about the situation in Gaza have made him a target. He’s gotten voicemails wondering why a Weizmann professor is so sympathetic to Palestine, and once when he returned from a trip, someone had tucked an Israeli army beret into the door handle of his car. Last year, he says, political opponents even went after his science by filing a complaint that his research was illegal.

What is clear is that Hanna, who is gregarious and attentive, has worked to cultivate a large group of friends and allies, including religious authorities—all part of a campaign to explain the science and hear out other views. He says he got a perfect grade in a bioethics class with a rabbi, conferenced with a priest from his hometown in Galilee, and even paid his respects to an Orthodox professor at a conservative hospital in Jerusalem. “It was unofficial. I didn’t have to get a permit from him,” Hanna says. “But … what does he think? Can I get him on board? Do I get a different opinion?” 

“I really do think it’s admirable that he is willing to ask these hard questions about what it is that he’s doing. I think that makes him different,” says Snead. “But if you are cynical, you could ask if his focus on the ethical dimension of this is more of a branding exercise.” Perhaps, Snead says, it’s a way to market the structures as the “green, sustainable alternative to embryos.”

A heartbeat in a jar

To admirers, Hanna is a doctor and researcher “heads above the rest,” according to Eli Adashi, the former dean of Brown University’s medical school. “He’s very unusual, very special, and is making major discoveries that can’t be ignored,” Adashi says. “He’s one of those unusually talented people that exceed the capacity of us mortals, and it all emanates from a town in Galilee that no one knows exists.”

While it is something of a rarity for a Palestinian to rise so high in Israel’s ivory tower, in reality Hanna has an elite background—he’s from a family of MDs, and an uncle, Nabil Hanna, co-developed the first antibody drug for cancer, the blockbuster rituximab.

Since the October 7 attack on Israel by Hamas, Israel has been at war in Gaza, and Hanna’s team has felt the effects. One young scientist dropped his pipette to don an IDF uniform. Another trainee, who is from Gaza, had a brother and other family members struck dead by an Israeli missile that hit near a church where people were sheltering. Then, this June, an Iranian ballistic missile hit the grounds of the Weizmann Institute, shattering windows and walls and sending Hanna’s students scrambling to save research. 

Despite delays in his research due to the ongoing conflict, Hanna’s ideas and technologies are being exported—and emulated. One place to see a version of the artificial womb is at the Janelia Research Campus, in Virginia, where one of Hanna’s former students, Alejandro Aguilera Castrejón, now operates a lab of his own. Aguilera Castrejón, for whom science was a ticket out of the poor outskirts of Mexico City, has tattoos from his wrists to his elbows; the newest depicts a hydra, a sea polyp noted for being able to regenerate itself from a few cells.

During a visit in June, Aguilera Castrejón flipped aside a black cover to reveal the incubator: a metal wheel that slowly turned, gently agitating jars filled with blood serum. Inside one, a mouse embryo drifted—a tiny, translucent shape, curved like a comma. Then, awesomely, a red-colored blob expanded in its center. A heartbeat. 

That day, it was a normal mouse embryo in the jar—it had been transferred there to see how far it would grow. Aguilera Castrejón has the goal of eventually birthing a mouse from an incubator, a process called ectogenesis. But the stem-cell embryos don’t grow as well or as long, he says. The problem isn’t just the challenge of growing them in culture jars. There’s probably some kind of fundamental disorganization. They aren’t entirely normal—not yet true embryos.

Aguilera Castrejón, who spent eight years at Weizmann contributing to Hanna’s research, is skeptical that the human version of the technology is ready for commercialization. For one thing, it’s inefficient. In every 100 attempts to make a synthetic embryo, the desired structure will form only once or twice. The rest are disorganized blobs—closer to “huevos fritos” than real embryos, he says. “I do think the human embryo model will go further, but it could take years,” he adds.

In Aguilera Castrejón’s view, Hanna is well placed to lead that work. One reason is that Israel offers a relatively permissive environment—and so does Jewish thought. In the Talmud, the embryo is considered “mere water” until the 40th day. Plus, Hanna is already successful. “Some people aren’t allowed to do it. And some people want to do it, but they can’t,” says Aguilera Castrejón. “Jacob wants to make it as realistic as possible and go as far as possible—that is his aim. He’s very ambitious and wants to tackle very big things people don’t dare to do. He really wants to do something big. His main aim is always to grow them as far as you can.” 

The first payoff of a technology for mimicking embryos this way is a new view of the unfolding human no one has ever had before. Real human embryos are rarely seen at the early stages, since they’re inside the womb—and at four or five weeks, many people don’t even know they’re pregnant. It’s been a black box. But synthetic models of the embryo can be made in the thousands (depending on the type), studied closely, inspected with modern microscopes, and subjected to dyes and genetic engineering tools, all while they’re still alive. Add a known toxic chemical that causes birth defects, like thalidomide, and you can closely trace the effects. “Since we don’t have a way to peer into the uterus, this allows us to watch things as if they are intrauterine but are not,” says Adashi, the former Brown dean and a fertility doctor. 

What’s more, a synthetic embryo may be able to make cells correctly—just as a real one does—and make all types at once, expanding on the limited few that scientists can create from stem cells today. While not all embryonic material is useful to medicine, the blood-forming cells in an embryo are known to be particularly potent. In mice, they can be extracted and multiplied—and if transplanted into a mouse subjected to lethal radiation, they will save it. 

Hanna imagines a cancer patient who needs a bone marrow transplant but can’t find a match. Could blood-forming cells be harvested from, say, 100 or 500 embryo-stage clones of that person, providing perfectly matched tissue? 

In his cost-benefit analysis, he believes the chance to save lives outweighs the moral risk of growing embryo models for a month, which is about how long it takes for key blood cells to form. At that stage, says Hanna, he thinks “there is still no personification of the embryo” and it’s permissible to use them in research.

Young everything

Hanna cofounded Renewal in 2022 with Omri Amirav-Drory, a venture capitalist whose fund, NFX, raised about $9 million for the company and purchased rights to Weizmann patents. The startup’s idea is to create synthetic embryos from the cells of patients, allowing them to grow for weeks or months to produce what Amirav-Drory calls “perfect cells” for transplant. That is because the synthetic structure, as a clone, would contain “young, genetically identical everything.”

Speaking at an event for tech futurists last year near San Francisco, Amirav-Drory flashed a picture of pregnancy tests used on the synthetic embryos. “We even went to CVS,” he said, “and by day eight it’s already triggering a pregnancy test. So it’s alive.”  

Amirav-Drory is a fan of Peter F. Hamilton, the science fiction author whose Commonwealth series features a society where space colonists transfer their minds into cloned bodies, attaining second lives. And he’s pitched Hanna’s technology along related lines, as a new type of longevity medicine based on replacing old cells with young ones. He is convinced Hanna’s work is “magic” that’s sure to win a Nobel.

“The importance of getting rid of the head is all ethical. It just means we can make all these bodies and organ structures without having to cross ethical lines or harm sentient living beings.”

Carsten Charlesworth, researcher, Stanford University

But he knows the startup has both technical and ethical challenges. The technical challenge is that once the synthetic embryos reach a certain size and age, the incubator can’t support them any longer. That’s because they lack a blood supply and need to absorb oxygen and nutrients from their surroundings; they starve once they get too big. One idea being considered is to add a feeding tube, but that involves microsurgery and isn’t easily scalable. The ethical issue is also age related: The more developed they become, the more they will be recognizably human, with the beginnings of organs and small, webbed fingers and toes. “No one has a problem with day 14, but the further we go, the further it looks like a baby, and we get into trouble. So how do we solve that?” Amirav-Drory asked a different audience, in Menlo Park.

The solution, so far, is a neural knockout—genetic changes made to the embryoids so they don’t develop a brain. The group has already tried out the concept on mice, removing a gene called LIM-1. That yielded a headless mouse, which looks a bit like a pink thumb, except with little claws and a tail. Those mice won’t live after birth, but they can develop in the womb. “We got synthetic mouse embryos growing with no head, with no brain,” Amirav-Drory said in Menlo Park. “It’s just to show you where we can go to solve both technical and ethical issues.” 

The idea of brain removal is a surprisingly active area of research—suggesting that it’s no sideshow. Working with mice, for example, Nakauchi’s team at Stanford is currently testing several different genetic changes to see if they can consistently yield an animal with no brain or head, but whose other tissues are normal. “The importance of getting rid of the head is all ethical. It just means we can make all these bodies and organ structures without having to cross ethical lines or harm sentient living beings,” says Carsten Charlesworth, a researcher in Nakauchi’s lab. He says the group is working toward a “genetic software package” it can add to mouse embryos to create a “reproducible phenotype.”

It may seem surprising that a technique designed to call forth a living being from stem cells is, simultaneously, being paired with a tactic to diminish that being. To Douglas Kysar, a professor at Yale Law School, that’s part of a broader trend toward what he calls “life that is not life,” which includes innovations like lab-grown meat. In the areas of animal-rights law Kysar studies, commercial biotech projects have begun to explore what he terms “disenhancement” and “disengineering.” That is the use of genetics to reduce the capacity of animals to suffer, feel pain, or have conscious experience at all, typically as part of a program to increase the efficiency and ethics of food production. 

For humans, of course, the worry around genetic engineering is usually that it will be used for enhancement—creating a baby with advantages. It’s much harder to think of examples where genetic disenhancements get pointed at the human embryo. John Evans, who co-directs the Institute of Applied Ethics at the University of California, San Diego, told me he can think of one, in literature. Hanna’s plans remind him of Bokanovsky’s Process, the fictional method of producing clones of different intelligence levels in the 1932 novel Brave New World.

That may not be a complete turnoff to investors. Lately, the plots of science fiction dystopias—Jurassic Park, Gattaca—seem to be getting repurposed at hot biotech properties. There’s Colossal, the company that wants to re-create extinct animals. Aguilera Castrejón says he’s already had a high-dollar offer to pack up his academic lab and join a startup company that wants to build an artificial womb. And when Hanna was at the Global Observatory meeting near Boston ​earlier this year, he was being shadowed by Matt Krisiloff, CEO of the Silicon Valley company Conception, which was set up to try to manufacture human eggs in the lab and has funding from OpenAI leader Sam Altman.

Eggs are another cell type that has proved difficult to generate from a stem cell in the lab. But a growing fetus will  form millions of immature egg cells. So just imagine: Someone too old to conceive gives some blood, which is converted into stem cells and then into a clone, from which the fetal gonad is dissected. Maybe the reproductive cells found there could be matured further in the lab. Or maybe those young and perfectly matched ovaries—her ovaries, really, not anyone else’s—could be returned to her body to finish developing. A fertility expert, David Albertini, told me it might just be possible.

During the ethics meeting he traveled to the US in May to attend, Hanna participated on a panel whose topic was “sources of moral authority.” Hanna’s authority comes from the possible benefits the science of synthetic embryos may bring. But he also wields his moral credibility. Early in his remarks, Hanna had framed the whole matter in a way that made worrying about what’s in the petri dish start to sound silly. Wearing a keffiyeh around his shoulders, he said: “I’d like to start and, you know, just remind everyone, unfortunately, that there is a genocide ongoing right now in Gaza, where children are being starved intentionally. And it is relevant, because we’re sitting here and we’re discussing human dignity, we’re discussing the status of an embryo, and we’re discussing the status of a fetus. But what about the life of the children, and adults, and innocent adults? How does it relate?”

Science Corporation—a competitor to Neuralink founded by the former president of Elon Musk’s brain-interface venture—has leapfrogged its rival after acquiring, at a fire-sale price, a vision implant that’s in advanced testing,.

The implant produces a form of “artificial vision” that lets some patients read text and do crosswords, according to a report published in the New England Journal of Medicine today.

The implant is a microelectronic chip placed under the retina. Using signals from a camera mounted on a pair of glasses, the chip emits bursts of electricity in order to bypass photoreceptor cells damaged by macular degeneration, the leading cause of vision loss in elderly people.

“The magnitude of the effect is what’s notable,” says José-Alain Sahel, a University of Pittsburgh vision scientist who led testing of the system, which is called PRIMA. “There’s a patient in the UK and she is reading the pages of a regular book, which is unprecedented.”  

Until last year, the device was being developed by Pixium Vision, a French startup cofounded by Sahel, which faced bankruptcy after it couldn’t raise more cash.  

That’s when Science Corporation swept in to purchase the company’s assets for about €4 million ($4.7 million), according to court filings.

“Science was able to buy it for very cheap just when the study was coming out, so it was good timing for them,” says Sahel. “They could quickly access very advanced technology that’s closer to the market, which is good for a company to have.”

Science was founded in 2021 by Max Hodak, the first president of Neuralink, after his sudden departure from that company. Since its founding, Science has raised around $290 million, according to the venture capital database Pitchbook, and used the money to launch broad-ranging exploratory research on brain interfaces and new types of vision treatments.

“The ambition here is to build a big, standalone medical technology company that would fit in with an Apple, Samsung, or an Alphabet,” Hodak said in an interview at Science’s labs in Alameda, California in September. “The goal is to change the world in important ways … but we need to make money in order to invest in these programs.”

By acquiring the PRIMA implant program, Science effectively vaulted past years of development and testing. The company has requested approval to sell the eye chip in Europe and is in discussions with regulators in the US.

Unlike Neuralink’s implant, which records brain signals so paralyzed recipients can use their thoughts to move a computer mouse, the retina chip sends information into the brain to produce vision. Because the retina is an outgrowth of the brain, the chip qualifies as a type of brain-computer interface.

Artificial vision systems have been studied for years and one, called the Argus II, even reached the market and was installed in the eyes of about 400 people. But that product was later withdrawn after it proved to be a money-loser, according to Cortigent, the company that now owns that technology.

Thirty-eight patients in Europe received a PRIMA implant in one eye. On average, the study found, they were able to read five additional lines on a vision chart—the kind with rows of letters, each smaller than the last. Some of that improvement was due to what Sahel calls “various tricks” like using a zoom function, which allows patients to zero in on text they want to read.

The type of vision loss being treated with the new implant is called geographic atrophy, in which patients have peripheral vision but can’t make out objects directly in front of them, like words or faces. According to Prevent Blindness, an advocacy organization, this type of central vision loss affects around one in 10 people over 80.  

The implant was originally designed starting 20 years ago by Daniel Palanker, a laser expert and now a professor at Stanford University, who says his breakthrough was realizing that light beams could supply both energy and information to a chip placed under the retina. Other implants, like Argus II, use a wire, which adds complexity.

“The chip has no brains at all. It just turns light into electrical current that flows into the tissue,” says Palanker. “Patients describe the color they see as yellowish blue or sun color.”

The system works using a wearable camera that records a scene and then blasts bright infrared light into the eye, using a wavelength humans can’t see. That light hits the chip, which is covered by “what are basically tiny solar panels,” says Palanker. “We just try to replace the photoreceptors with a photo-array.”

The current system produces about 400 spots of vision, which lets users make out the outlines of words and objects. Palanaker says a next-generation device will have five times as many “pixels” and should let people see more: “What we discovered in the trial is that even though you stimulate individual pixels, patients perceive it as continuous. The patient says ‘I see a line,’ “I see a letter.’”

Palanker says it will be important to keep improving the system because “the market size depends on the quality of the vision produced.”

When Pixium teetered on insolvency, Palanker says, he helped search for a buyer, meeting with Hodak. “It was a fire sale, not a celebration,” he says. “But for me it’s a very lucky outcome, because it means the product is going forward. And the purchase price doesn’t really matter, because there’s a big investment needed to bring it to market. It’s going to cost money.”  

During a visit to Science’s headquarters, Hodak described the company’s effort to redesign the system into something sleeker and more user-friendly. In the original design, in addition to the wearable camera, the patient has to carry around a bulky controller containing a battery and laser, as well as buttons to zoom in and out. 

But Science has already prototyped a version in which those electronics are squeezed into what look like an extra-large pair of sunglasses.

“The implant is great, but we’ll have new glasses on patients fairly shortly,” Hodak says. “This will substantially improve their ability to have it with them all day.” 

Other companies also want to treat blindness with brain-computer interfaces, but some think it might be better to send signals directly into the brain. This year, Neuralink has been touting plans for “Blindsight,” a project to send electrical signals directly into the brain’s visual cortex, bypassing the retina entirely. It has yet to test the approach in a person.

A team at Microsoft says it used artificial intelligence to discover a “zero day” vulnerability in the biosecurity systems used to prevent the misuse of DNA.

These screening systems are designed to stop people from purchasing genetic sequences that could be used to create deadly toxins or pathogens. But now researchers led by Microsoft’s chief scientist, Eric Horvitz, say they have figured out how to bypass the protections in a way previously unknown to defenders. 

The team described its work today in the journal Science.

Horvitz and his team focused on generative AI algorithms that propose new protein shapes. These types of programs are already fueling the hunt for new drugs at well-funded startups like Generate Biomedicines and Isomorphic Labs, a spinout of Google. 

The problem is that such systems are potentially “dual use.” They can use their training sets to generate both beneficial molecules and harmful ones.

Microsoft says it began a “red-teaming” test of AI’s dual-use potential in 2023 in order to determine whether “adversarial AI protein design” could help bioterrorists manufacture harmful proteins. 

The safeguard that Microsoft attacked is what’s known as biosecurity screening software. To manufacture a protein, researchers typically need to order a corresponding DNA sequence from a commercial vendor, which they can then install in a cell. Those vendors use screening software to compare incoming orders with known toxins or pathogens. A close match will set off an alert.

To design its attack, Microsoft used several generative protein models (including its own, called EvoDiff) to redesign toxins—changing their structure in a way that let them slip past screening software but was predicted to keep their deadly function intact.

The researchers say the exercise was entirely digital and they never produced any toxic proteins. That was to avoid any perception that the company was developing bioweapons. 

Before publishing the results, Microsoft says, it alerted the US government and software makers, who’ve already patched their systems, although some AI-designed molecules can still escape detection. 

“The patch is incomplete, and the state of the art is changing. But this isn’t a one-and-done thing. It’s the start of even more testing,” says Adam Clore, director of technology R&D at Integrated DNA Technologies, a large manufacturer of DNA, who is a coauthor on the Microsoft report. “We’re in something of an arms race.”

To make sure nobody misuses the research, the researchers say, they’re not disclosing some of their code and didn’t reveal what toxic proteins they asked the AI to redesign. However, some dangerous proteins are well known, like ricin—a poison found in castor beans—and the infectious prions that are the cause of mad-cow disease.

“This finding, combined with rapid advances in AI-enabled biological modeling, demonstrates the clear and urgent need for enhanced nucleic acid synthesis screening procedures coupled with a reliable enforcement and verification mechanism,” says Dean Ball, a fellow at the Foundation for American Innovation, a think tank in San Francisco.

Ball notes that the US government already considers screening of DNA orders a key line of security. Last May, in an executive order on biological research safety, President Trump called for an overall revamp of that system, although so far the White House hasn’t released new recommendations.

Others doubt that commercial DNA synthesis is the best point of defense against bad actors. Michael Cohen, an AI-safety researcher at the University of California, Berkeley, believes there will always be ways to disguise sequences and that Microsoft could have made its test harder.

“The challenge appears weak, and their patched tools fail a lot,” says Cohen. “There seems to be an unwillingness to admit that sometime soon, we’re going to have to retreat from this supposed choke point, so we should start looking around for ground that we can actually hold.” 

Cohen says biosecurity should probably be built into the AI systems themselves—either directly or via controls over what information they give. 

But Clore says monitoring gene synthesis is still a practical approach to detecting biothreats, since the manufacture of DNA in the US is dominated by a few companies that work closely with the government. By contrast, the technology used to build and train AI models is more widespread. “You can’t put that genie back in the bottle,” says Clore. “If you have the resources to try to trick us into making a DNA sequence, you can probably train a large language model.”