This study investigates the origin, fate, and dynamics of non-parenchymal macrophages at the interfaces of the central nervous system (CNS), including perivascular, meningeal, and choroid plexus macrophages. Using single-cell RNA-sequencing, the authors find that these macrophages share a molecular profile with microglia but differ from monocytes. They demonstrate that CNS macrophages arise from yolk sac precursors during embryonic development and remain stable over time. The transcription factor Pu.1 is essential for their generation, while myb, Baf3, and Nr4a1 are not required. During autoimmune inflammation, CNS macrophages undergo extensive self-renewal through local proliferation rather than recruitment of peripheral monocytes. The study provides new insights into the transcriptional networks, ancestry, and dynamics of CNS macrophages, highlighting their distinct specialization compared to microglia and monocytes.This study investigates the origin, fate, and dynamics of non-parenchymal macrophages at the interfaces of the central nervous system (CNS), including perivascular, meningeal, and choroid plexus macrophages. Using single-cell RNA-sequencing, the authors find that these macrophages share a molecular profile with microglia but differ from monocytes. They demonstrate that CNS macrophages arise from yolk sac precursors during embryonic development and remain stable over time. The transcription factor Pu.1 is essential for their generation, while myb, Baf3, and Nr4a1 are not required. During autoimmune inflammation, CNS macrophages undergo extensive self-renewal through local proliferation rather than recruitment of peripheral monocytes. The study provides new insights into the transcriptional networks, ancestry, and dynamics of CNS macrophages, highlighting their distinct specialization compared to microglia and monocytes.