The aging human brain is fascinating, because in some ways, it improves with age – but we generally hear more about how it declines. Previous research has shown that some of the seemingly inevitable declines in brain health, often seen in 70- and 80-year old brains, start in midlife. The study wasn't designed to explain why they occur, but the findings hint that the aging hippocampus may follow different aging trajectories in males and females. They analyzed postmortem brain tissue, providing snapshots from different people, who obviously lived different lives and had different genes. Still, by combining ways of analyzing and understanding brain aging, this study raises the possibility that our brains undergo far more cellular remodeling during aging than previously imagined.