In this study, the authors reported a variety of new aging-associated phenotypic changes of the primate hippocampus, including increased DNA damage and heterochromatin erosion with time, alongside loss of proteostasis and elevated inflammation. They also established the first single-nucleus transcriptomic atlas of primate hippocampal aging, finding that neural transiently amplifying progenitor cell (TAPC) and microglia were most affected by aging. In-depth dissection of gene-expression dynamics revealed impaired TAPC division and compromised neuronal function along the neurogenesis trajectory; while elevated pro-inflammatory responses in the aged microglia and oligodendrocyte, as well as dysregulated coagulation pathways in the aged endothelial cells contribute to a hostile microenvironment for neurogenesis.