What Happened When Scientists Grew Mini-Brains for Five Years

Story by CuriosiTEA JC Team

Original Research Article: Faravelli, Antón-Bolaños et al., Nature, 2026.Journal link: https://doi.org/10.1038/s41586-026-10877-x

Scientists grew tiny models of the human brain for more than five years. These models are called organoids. They are made from human stem cells and grown in a dish. The organoids did not stop developing after a few months. They kept getting older, and the older cells even seemed to remember how much time had passed.

The human brain takes almost twenty years to finish growing. Most of that happens after a baby is born. Scientists cannot look inside a living person's brain to watch it. Mice grow up too fast to copy the human pace. That leaves a big gap in what we know.

Most organoid studies stop after a few months. So the scientists asked: can brain organoids keep growing for years, and can they track time like a real brain?

The team grew organoids for over five years. They read the active genes in about 425,000 cells. They also measured chemical tags that build up on DNA as a body ages. Scientists use these tags like a clock. Both tests agreed. The organoids aged steadily, and the clock matched how long they had really been growing.

One problem came up. The neurons, the cells that send signals, kept dying. So the team switched to a liquid that lets neurons stay electrically active. This time the neurons lived. They grew more connections and fired together for at least two years.

Then came the strangest part. The scientists mixed young cells with cells from nine month old organoids. The old cells started making neurons again, but they skipped ahead. In two weeks they built a late type of neuron that normally takes months. The young cells right next to them made only early cell types. The old cells had not forgotten what they already built.

Now scientists have a way to study brain growth after birth. Many conditions show up in childhood and the teen years, so that period matters. Next they want to add things a real brain has but a dish does not, like blood vessels and signals from the senses.

Student Reflection: What surprised us most was that old cells could skip steps instead of starting over, because we thought development had to go in order. A question we still have is whether the organoids would keep aging past five years. This connects to the real world because many brain conditions appear in kids and teens, and now there is a model that reaches that age.