An international team of researchers has created a full-cell atlas of a mammalian brain, providing a detailed map of the mouse brain with information on over 32 million cells. This groundbreaking atlas describes the types, location, and connectivity of cells, as well as their transcriptome and epigenome. It serves as a blueprint for understanding human brain function and developing precision treatments for mental and neurological illnesses. The atlas also reveals the neurotransmitters used by different cells and the relationship among cell types, offering insights into brain circuitry and function.