This study presents a comprehensive single-cell RNA sequencing (scRNA-seq) analysis of the human brain vasculature, covering fetal, adult, and diseased states. The researchers analyzed 606,380 endothelial cells, perivascular cells, and other tissue-derived cells from 117 samples, including 68 human fetuses and adult patients with various brain pathologies. They identified extensive molecular heterogeneity in the vasculature of healthy fetal and adult brains and across five vascular-dependent central nervous system (CNS) pathologies, such as brain tumors and vascular malformations. Key findings include altered arteriovenous (AV) differentiation, reactivation of fetal programs in diseased vasculature, upregulation of MHC class II molecules, and strong endothelial-to-perivascular cell ligand-receptor cross-talk. The study provides insights into the molecular architecture and heterogeneity of the developing, adult, and diseased human brain vasculature, offering a valuable reference for future research.This study presents a comprehensive single-cell RNA sequencing (scRNA-seq) analysis of the human brain vasculature, covering fetal, adult, and diseased states. The researchers analyzed 606,380 endothelial cells, perivascular cells, and other tissue-derived cells from 117 samples, including 68 human fetuses and adult patients with various brain pathologies. They identified extensive molecular heterogeneity in the vasculature of healthy fetal and adult brains and across five vascular-dependent central nervous system (CNS) pathologies, such as brain tumors and vascular malformations. Key findings include altered arteriovenous (AV) differentiation, reactivation of fetal programs in diseased vasculature, upregulation of MHC class II molecules, and strong endothelial-to-perivascular cell ligand-receptor cross-talk. The study provides insights into the molecular architecture and heterogeneity of the developing, adult, and diseased human brain vasculature, offering a valuable reference for future research.