I’m going to let you in on a secret. Every cell in your body has the potential to get smarter. I don’t mean this metaphorically, or in a “body keeps the score” kind of way. I mean that if lab-coated biologists took a sample of your skin and very carefully manipulated the cells inside it, they could actually make a brain. They do it all the time.
Not a brain as complex as the one behind your eyes, of course, but a glob of gray matter nonetheless, with a few-million-odd neurons that can send and receive electrical signals. Biologists call these strange creations human brain organoids. Kept at a womblike 98.6 degrees Fahrenheit for eight months, they’ll produce repetitive oscillations—brain waves—nearly indistinguishable from those made by a premature baby.
In cell culture labs around the world, human brain organoids live out their short lives as neural guinea pigs, testing the effects of diseases, toxins, and new pharmaceuticals. But they may soon be on to more glamorous pursuits. At the University of San Diego, organoids are guiding spidery robots through mazes and taking hero doses of psychedelics. At Johns Hopkins, they’re forming the basis of novel biocomputing systems. And at a startup in Melbourne, they’re playing video games like Pong and Doom.
Biologists do the darnedest things. While the rest of us are distracted by large language models and AI agents, they’re going straight to the source of intelligence, cultivating living neurons and teaching themselves to program them with electrical signals and hits of dopamine. In the future, they wager, artificial intelligence won’t be artificial at all. It’ll be built from the stuff of life itself.
The most metal building at UC San Diego is the library. An inverted concrete ziggurat, the Geisel Library—named for the children’s author better known as Dr. Seuss—looms over an otherwise bucolic campus on spindly, two-story legs. On a recent afternoon, as a marine layer hung low in the eucalyptus groves, it looked particularly like the mothership of a brutalist alien race.
That day, the Geisel’s sunken lobby was hung with scientific images from the university’s collection. Among CGI renderings of folded proteins and macrophotographs of benthic sea creatures, one image stuck out. It depicted a clump of human brain cells, silhouetted in black against the milky white of a petri dish. A corona of axons, the threadlike nerve endings that transmit electrical impulses across the brain, stretched outward from the clump with palpable yearning.
Whether in our skulls or in a dish, neurons want nothing more than to find one another—and, across the emptiness, to forge the synapses whose electrical chattering forms the basis of thought. They’re very good at it. If you put loose brain cells together, they will multiply and interlink until they’ve cohered into autonomous globs of tissue. Human brain organoids practically make themselves.
A 20-minute walk from the Geisel, at UCSD’s Sanford Stem Cell Institute, they’re making themselves in the tens of thousands. “Whatever environment you put them in, the first thing that they do is try to connect,” said the Brazilian developmental biologist Alysson Muotri, as we gazed over the blue plane of Pacific outside his office window. “Connect with the dishes, connect with the electrodes, connect to each other. This is an intrinsic property of our brain, to connect.”
Muotri is dashing, with a surfer’s tan and the aquiline profile of a figure on an ancient Roman coin. Over the past decade, his lab has dramatically expanded the scope of brain organoid research. He and his colleagues have revived genetic material from the hominin fossil record to create “Neanderthalized” brain organoids. They have sent organoid payloads to the International Space Station to study what cosmic radiation does to astronaut brains. But the issue closest to Muotri’s heart is autism. His 18-year-old son is autistic and receives 24-hour care. By studying brain organoids grown from the cells of autistic donors—including his son—he hopes to pinpoint where the neural development of autistic children differs from their neurotypical counterparts.