Scientists Grew Human Brain Organoids for Years and Discovered They Keep Track of Time

Scientists grew human brain organoids for almost six years and discovered they keep track of time, according to a recent study published in *Nature*. The organoids, developed by a team funded by the National Institutes of Health (NIH), were sustained for over five years, far longer than previous efforts. The research revealed that the organoids exhibited a developmental clock similar to that found in real brains, which could help researchers study later stages of human brain development and neurological conditions that develop over time. The organoids were able to maintain their developmental milestones, including neuron formation and maturation, over extended periods, and their biological clocks closely matched those observed in human brains.

• The organoids were maintained for almost six years, far longer than previous efforts.
• The team tracked biological age and gene expression by observing chemical changes to the genome and examining cellular characteristics down to the level of individual cells.
• The organoids developed outside the human body but matured at a similarly slow pace, and neurons continued establishing connections and displaying electrical activity for years.
• The researchers attributed the organoids' ability to maintain activity to a specialized fluid designed to support long-term neuronal function.
• The organoids were transplanted with neurons from different ages and retained their developmental characteristics, suggesting they recorded and recalled the time they had spent in culture.
• The study highlights the potential of organoids to model complex brain development and reveal mechanisms of human brain maturation.
• The paper, "Human Brain Organoids Record the Passage of Time over Multiple Years," appeared in *Nature* on August 19, 2026.

AI-generated summary of the original article — see the source for the full story.