This scientist rewarmed and studied pieces of his friend’s cryopreserved brain | MIT Technology Review

You need to enable JavaScript to view this site.

Skip to ContentMIT Technology ReviewFeaturedTopicsNewslettersEventsAudioMIT Technology ReviewFeaturedTopicsNewslettersEventsAudioBiotechnology and healthThis scientist rewarmed and studied pieces of his friend’s cryopreserved brainA gerontologist wanted his preserved brain to be reanimated. Cryopreservation is more likely to be used on organs for transplantation.
By Jessica Hamzelouarchive pageMarch 24, 2026Stephanie Arnett/MIT Technology Review | Adobe Stock L. Stephen Coles’s brain sits cushioned in a vat at a storage facility in Arizona. It has been held there at a temperature of around −146 degrees °C for over a decade, largely undisturbed. That is, apart from the time, a little over a year ago, when scientists slowly lifted the brain to take photos of it. Years before, the team had removed tiny pieces of it to send to Coles’s friend. Coles, a researcher who studied aging, was interested in cryogenics—the long-term storage of human bodies and brains in the hope that they might one day be brought back to life. Before he died, he asked cryobiologist Greg Fahy to study the effects of the preservation procedure on his brain. Coles was especially curious about whether his cooled brain would crack, says Fahy. Related StoryMeet the Vitalists: the hardcore longevity enthusiasts who believe death is “wrong”Read next Coles’s brain was preserved shortly after he died in 2014, but Fahy has only recently got around to analyzing those samples. He says that Coles’s brain is “astonishingly well preserved.” “We can see every detail [in the structure of the brain biopsies],” says Fahy, who is chief scientific officer at biotech companies Intervene Immune and 21st Century Medicine (where he is also executive director). He hopes this means that Coles’s brain still stands a chance of reanimation at some point in the future.
Other cryobiologists are less optimistic. “This brain is not alive,” says John Bischof, who works on ways to cryopreserve human organs at the University of Minnesota. Still, Fahy’s research could help provide a tool to neuroscientists looking for new ways to study the brain. And while human reanimation after cryopreservation may be the stuff of science fiction, using the technology to preserve organs for transplantation is within reach.
Banking a brain Coles, a gerontologist who spent the latter part of his career studying human longevity, opted to have his brain cryogenically preserved when he died of pancreatic cancer. After he was declared dead, Coles’s body was kept at a low temperature while he was transferred to Alcor, a cryonics facility in Arizona. His head was removed from his body, and a team perfused his brain with “cryoprotective” chemicals that would prevent it from freezing. They then removed it from his skull and cooled it to −146 °C. Related StoryWhy the sci-fi dream of cryonics never diedRead next Coles had another request. As a scientist, he wanted his cryopreserved brain to be studied. Hundreds of people have opted to have their brains—with or without the rest of their bodies—stored at cryonic facilities (the remains of 259 individuals are currently stored as either whole bodies or heads at Alcor). But scientists know very little about what has happened to those brains, and there’s no evidence to suggest they could be revived. Coles had met Fahy through their shared interest in longevity, and he asked him to investigate. “He thought that if he had himself cryopreserved, we could learn from his brain whether cracking was going to happen or not,” says Fahy. That’s what typically happens when organs are put into liquid nitrogen at −196 °C, he says. The extreme cooling creates “tension in the system,” he says. “If you tap it, it’ll just shatter.” This cracking is less likely at the slightly warmer temperatures used for preservation.  Fahy was involved from the time the samples were taken. “We had Greg Fahy on the phone coordinating the whole thing, [including] where the biopsies were taken,” says Nick Llewellyn, who oversees research at Alcor. (Llewellyn was not at Alcor at the time but has discussed the procedure with his colleagues.) The biopsied samples were stored in liquid nitrogen and earmarked for Fahy. The rest of the brain was cooled and kept in a temperature-controlled storage container at Alcor. Bouncing back It wasn’t until years later that Fahy got around to studying those biopsies. He was interested in how the cryoprotectant—which is toxic—might have affected the brain cells. Previous research has shown that flooding tissues with cryoprotectant can distort the structure of cells, essentially squashing them. It’s one of the many challenges facing cryobiologists interested in storing human tissues at very low temperatures. While the vitrification of eggs and embryos—which cools them to −196 °C and essentially turns them to glass—has become relatively routine (thanks in part to Fahy’s own work on mouse embryos back in the 1980s), preserving whole organs this way is much harder. It is difficult to cool bigger objects in a uniform way, and they are prone to damaging ice crystal formation, even when cryoprotectants are used, as well as cracking.

Fahy found that when he rewarmed and rehydrated Coles’s brain cells, their structure seemed to bounce back to some degree. Fahy demonstrated the effect over a Zoom call: “It looks like this,” he said with his hands as if in prayer, “and it goes back to this,” he added, connecting his forefingers and thumbs to create a triangle shape. The structure of the tissue looks pretty intact, too, to him at least, though he admits a purist expecting a pristine structure would be disappointed. He and his colleagues have been able to see remarkable details in the cells and their component parts. “There’s nothing we don’t see,” says Fahy, who has shared his results, which have not yet been peer reviewed, at the preprint server bioRxiv. “It seems that [by taking the cryogenic approach] you can preserve everything.” As for the cracking, “from what I was told, no cracks were observed [by the team that initially preserved the brain],” says Fahy. The team at Alcor took photographs of the brain when they took the biopsies, but the images were later lost due to a server malfunction, he says. In the more recent photos, the brain is covered in a layer of frost, which makes it impossible to see if there are any cracks, he adds. Attempts to remove the frost might damage the brain, so the team has decided to leave it alone, he says. Back to life? Fahy and his colleagues used chemicals to “fix” Coles’s brain samples once they had been rewarmed. That process is typically used to stop fresh tissue samples from decaying, but it also effectively kills them. But he thinks his results suggest that it might be possible to cryopreserve small pieces of brain tissue and reanimate them to learn more about how they work. Functional recovery seems to be possible in mice—a few weeks ago a team in Germany showed that they were able to revive brain slices that had been stored at −196 °C. Those brain samples showed electrical activity after being cooled and rewarmed. If cryobiologists can achieve the same feat with human brain samples, those samples could provide neuroscientists with new insights into how living brains work. Related StoryHow a volcanic eruption turned a human brain into glassRead next Brain cryopreservation “can capture a little bit more of the complexities of the brain,” says Shannon Tessier, a cryobiologist at Massachusetts General Hospital who is developing technologies to preserve hearts, livers, and kidneys for transplantation. “[Being] able to use human brains from deceased individuals [could] add another layer to the research tool kit,” she says. And Fahy’s paper shows “what happens when we try and vitrify a one-liter, dense, massive goop,” says Matthew Powell-Palm, a cryobiologist at Texas A&M University. “We now have a strong indication that quite large [tissues and organs] can be vitrified by perfusion [without forming too much ice],” he says.
All of the scientists I spoke to, including Fahy, are also working on ways to cool and preserve organs for transplantation. These are in short supply partly because once an organ is removed from a donor, it usually must be transplanted into its recipient within a matter of hours.  Cryopreservation could buy enough time to make use of more organs, find better organ-donor matches, and potentially even prepare recipients’ immune systems and save them from a lifetime of immunosuppressant drugs, says Bischof, who has also been developing new technologies for organ cryopreservation.
Bischof, Fahy, and others have made huge strides in their attempts so far, and they have managed to remove, cryopreserve, and transplant organs in rabbits and rats, for example. “We’re at the cusp of human-scale organ cryopreservation,” says Bischof. But when it comes to preserving brains, donation isn't the aim. Coles had hoped to be reanimated—a far more ambitious goal that hinges on the ability to restore brain function. Brain reanimation Fahy acknowledges that while the structure of Coles’s brain samples did bounce back, there is no evidence to suggest the cells could be brought back to life and regain electrical activity and a functioning metabolism. “Restoring it to function … that’s a whole other story,” he says. But he thinks that successful cryopreservation of the brain “is the gateway to human suspended animation, which [could allow] us to get to the stars someday.” Figuring out human preservation would also allow people to avoid death through what he calls “medical time travel”—journeying to an unspecified time in the future when science will have found a cure for whatever was due to kill that person. “That would be an ultimate goal to pursue,” he says. “I put the chances [of brain reanimation] at pretty low,” says Alcor’s own Llewellyn. “The kind of technology we need is practically unfathomable.” The brains already in storage at Alcor and other facilities have been preserved in ways that “have not been validated to work for reanimation,” says Tessier. An expectation that they’ll one day be brought back to life in some form is “quite a jump of faith and hope that’s not based on science,” she says. As Powell-Palm puts it: “There are so many ways in which those neurons could be toast.” by Jessica HamzelouShareShare story on linkedinShare story on facebookShare story on emailPopularA “QuitGPT” campaign is urging people to cancel their ChatGPT subscriptionsMichelle KimMoltbook was peak AI theaterWill Douglas HeavenHow Pokémon Go is giving delivery robots an inch-perfect view of the worldWill Douglas HeavenMeet the Vitalists: the hardcore longevity enthusiasts who believe death is “wrong”Jessica HamzelouDeep DiveBiotechnology and healthMeet the Vitalists: the hardcore longevity enthusiasts who believe death is “wrong”They argue we need a revolution—and more and more influential scientists, funders, and politicians are taking them seriously.
By Jessica Hamzelouarchive pageThe first human test of a rejuvenation method will begin “shortly” In a bid to treat blindness, Life Biosciences will try out potent cellular reprogramming technology on volunteers.
By Antonio Regaladoarchive pagePeptides are everywhere. Here’s what you need to know.The compounds have exploded in popularity, but big questions about safety and effectiveness are still unresolved.
By Cassandra Willyardarchive pageAn experimental surgery is helping cancer survivors give birthAt least eight babies have been born to patients who underwent the procedure.
By Jessica Hamzelouarchive pageStay connectedIllustration by Rose WongGet the latest updates fromMIT Technology ReviewDiscover special offers, top stories,
upcoming events, and more.Enter your emailPrivacy PolicyThank you for submitting your email!Explore more newslettersIt looks like something went wrong.
We’re having trouble saving your preferences.
Try refreshing this page and updating them one
more time. If you continue to get this message,
reach out to us at
customer-service@technologyreview.com with a list of newsletters you’d like to receive.The latest iteration of a legacyFounded at the Massachusetts Institute of Technology in 1899, MIT Technology Review is a world-renowned, independent media company whose insight, analysis, reviews, interviews and live events explain the newest technologies and their commercial, social and political impact.READ ABOUT OUR HISTORYAdvertise with MIT Technology ReviewElevate your brand to the forefront of conversation around emerging technologies that are radically transforming business. From event sponsorships to custom content to visually arresting video storytelling, advertising with MIT Technology Review creates opportunities for your brand to resonate with an unmatched audience of technology and business elite.ADVERTISE WITH US© 2026 MIT Technology ReviewAboutAbout usCareersCustom contentAdvertise with usInternational EditionsRepublishingMIT Alumni NewsHelpHelp & FAQMy subscriptionEditorial guidelinesPrivacy policyTerms of ServiceWrite for usContact uslinkedin opens in a new windowinstagram opens in a new windowreddit opens in a new windowfacebook opens in a new windowrss opens in a new window

L. Stephen Coles’s ambitious project, undertaken with cryobiologist Greg Fahy, centered on the cryopreservation of his own brain following his death from pancreatic cancer. Prior to his passing, Coles sought to investigate the effects of this preservation process, specifically whether cracking—a common issue with cryopreserved organs—would occur in his brain tissue. Fahy, chief scientific officer at Intervene Immune and 21st Century Medicine, took on this unusual request, meticulously studying the biopsied samples taken from Coles’s brain after it was cooled to −146 degrees Celsius and perfused with cryoprotective chemicals. Remarkably, the initial findings indicated that the brain tissue retained a significant degree of structural integrity upon rewarming and rehydration, exhibiting a degree of “bounce-back” in its cellular organization.

Fahy’s work, though preliminary and yet to be peer-reviewed, offered a potential tool for neuroscientists studying brain preservation and reanimation, despite the significant skepticism surrounding the feasibility of actually reviving the brain. Other cryobiologists, such as John Bischof at the University of Minnesota, expressed reservations, emphasizing that the brain was “not alive.” However, the research highlighted the challenges of cryopreservation, including the distortion of cellular structure caused by cryoprotectant chemicals and the risk of cracking due to the extreme cooling process. Fahy's earlier work on mouse embryos in the 1980s contributed to the understanding of vitrification techniques.

The focus remained on understanding the process itself, exploring whether the structural integrity observed could provide a basis for future research and potentially lead to advancements in brain preservation technology. Fahy's examination revealed details about the cells and their components, noting that “there’s nothing we don’t see.” Initially, the team observed that the structure of the tissue looked pretty intact, but any purist expecting a pristine structure would be disappointed. Notably, a server malfunction resulted in the loss of the initial photographs taken of the brain, including those documenting whether cracks had formed.

Despite the skepticism surrounding brain reanimation—a goal deemed “pretty low” by Fahy—the research had implications beyond the immediate ambition. Fahy’s work could apply to broader efforts in organ cryopreservation, particularly the potential to buy time for transplantation due to supply shortages, improve donor matching, and potentially eliminate the need for immunosuppressant drugs. Shannon Tessier at Massachusetts General Hospital recognized the value of using human brain samples—from deceased individuals—as a research tool, adding another layer to the existing toolkit. Matthew Powell-Palm at Texas A&M University noted that the findings indicated a strong indication that quite large tissues and organs can be vitrified without forming too much ice. Ultimately, L. Stephen Coles’s experiment, despite its philosophical aspirations, was becoming a valuable contributor to the field of cryobiology, offering insights that could impact both organ preservation and, perhaps one day, the long-held dream of suspended animation and, potentially, human time travel.