Scientists from Rockefeller University created a cell atlas of nearly 7 million cells from 21 tissues of mice in three age groups: young, middle-aged, and old.[1][2][4] The study revealed more than 1,800 different cell subtypes, some of which were previously undescribed.[1][2] About a quarter of all cell types change in number with age, for example, muscle and kidney cells decrease, while immune cells increase significantly.[1][2][4] These changes begin as early as 5 months of age, which is earlier than expected.[1] Similar changes in cell populations occur in a coordinated manner in different organs at the same time, suggesting systemic signals.[1][2] About 40% of the changes differ between men and women, for example women show stronger immune activation.[1][2] Research has identified shared genetic and epigenetic changes that could serve as targets for antiaging therapies.[1][2]