It has been proposed that the last parts of the brain to mature are the first to degenerate as we age. By analysing structural MRI data from 484 healthy participants aged from 8 to 85 years, Douaud et al. now provide direct evidence for this assertion. They reveal a network of brain regions that develop late in adolescence and degenerate first in old age. Furthermore, this network overlaps with those areas that are most vulnerable to changes in Alzheimer's disease or schizophrenia.