Lab-grown brain organoids on a glass slide CREDIT D.C.N. van der Heijden / UMC Utrecht

Brain Tissue Grown in a Dish Kept Track of Its Own Age for Five Years

Human brain tissue grown from stem cells kept maturing in culture for more than five years, following roughly the same timetable as a real brain. Chemical marks on its DNA recorded how long it had been growing, and older cells remembered which developmental steps they had already completed.