[Brain Cells. Photo Credit to Pixabay] 

On August 19, 2026, Nature published a study showing that human cortical organoids, laboratory-grown models of the brain’s outer layer, can survive and continue developing for more than five years.

More surprisingly, the organoids did not simply stay alive but continued to mature over time.

Changes in their gene activity and DNA also followed patterns associated with normal human brain development. 

Brain organoids are simplified models of the human brain.

Scientists can create them by reprogramming human cells into pluripotent stem cells and then guiding those cells to develop into neurons and other types of brain cells.

Brain organoids are particularly valuable tools because the human brain develops at a very slow pace.

Brain development begins before birth and continues for many years, but scientists cannot easily observe how individual brain cells change inside a living person over such a long period.

Until now, most brain organoid studies have focused mainly on early brain development because keeping organoids healthy for several years is difficult.

In the new study, Paola Arlotta and her research team at Harvard University and the Broad Institute analyzed 34 organoids that had been growing for between six months and five years.

By integration previous research data, they studied a total of 110 organoids and nearly 425,000 individual cells.

The results indicated that the organoids continued to mature instead of remaining at an early stage of development.

Their gene activity also changed in patterns that mirrored important stages of normal human brain development.

In other words, the organoids seemed to follow a kind of developmental clock.

However, this does not mean that an older organoid becomes the same as a real child's brain.

Brain organoids are much simpler than actual human brains, and the study only shows that some of their cells can follow parts of the normal human brain's developmental timeline.

Researchers also investigated DNA methylation, a chemical change to DNA that can be used to estimate the biological age of cells.

The biological ages predicted from these DNA changes closely matched how long the organoids had actually been growing in the laboratory.

Another experiment yielded an interesting result.

The researchers compared neural progenitor cells, which can later develop into neurons, from younger and older organoids.

When the cells were encouraged to produce new neurons, the older cells skipped some early developmental steps and quickly produced more mature neurons.

This suggested that the cells may retain a form of biological “memory” of the developmental stages they have already passed through.

The neurons inside the organoids also formed connections and generated electrical signals.

Researchers were able to observe this activity for at least two years.

This finding showed that the neurons were becoming more functionally mature, but electrical activity does not mean that brain organoids can think or are conscious.

Growing brain organoids for several years could give scientists a novel way to study long-term human brain development.

For example, researchers may be able to study how neurodevelopmental conditions such as autism begin and progress over time.

They could also examine how genetic changes or possible treatments affect human brain cells at different stages of development.

However, important limitations still exist.

Brain organoids do not contain all of the cell types, structures, and complex neural connections present in a real human brain.

They also develop outside the body, so they do not receive many of the signals that normally come from other organs and body systems.

Due to these differences, scientists cannot assume that everything observed in an organoid will happen in exactly the same way in a real human brain.

Time is another significant challenge.

Waiting several years for an organoid to reach later stages of development can make experiments slow and challenging.

As a result, researchers are seeking ways to reproduce later stages of brain development more quickly.

The most significant finding of this study is not that scientists created a complete human brain in the laboratory.

Rather, the study shows that human brain cells grown outside the body can continue to mature for years while following parts of the naturally slow developmental process of the human brain.

By modeling years of brain development in the laboratory, these organoids could give scientists access to stages of human brain development that were previously extremely difficult to study.

Could long-lasting brain organoids someday help scientists better understand how brain disorders originate and develop over time?