The central nervous system (CNS) hosts a variety of immune cells including two anatomically and transcriptionally distinct macrophage populations: microglia are found in the parenchyma, whereas CNS border-associated macrophages (CAMs) cover the CNS interfaces, such as the perivascular spaces and the meninges. Recent emergence of novel genetic tools and cutting-edge techniques including single-cell RNA-seq enables to study the CNS macrophages in more depth and have given novel insights into the origins, kinetics, functions, transcriptomic profiles, heterogeneity of microglia and CAMs. In this symposium, I will discuss our current knowledge of the characteristics of CNS macrophages.