Macrophages play an important role in maintaining brain tissue homeostasis. Brain macrophages are heterogeneous, exhibiting tissue-specific adaptations based on their location. Microglia are the macrophages found within the brain parenchyma, while border-associated macrophages (BAMs) reside in the brain’s border regions, such as the meninges, choroid plexus, and perivascular spaces. Our previous research has shown that BAMs are heterogeneous and transcriptionally distinct from microglia, underscoring the diversity of brain macrophages. Our current research aims to further delineate the identities and states of brain macrophages, identify the signals and gene regulatory networks driving their development and heterogeneity, and understand their role in maintaining brain homeostasis. We are also dedicated to understanding the role of macrophages in brain diseases, including primary brain cancer, neurodegenerative disorders like Alzheimer’s disease, and infectious brain diseases.”