The evolution of higher cognitive functions in humans has so far mostly been linked to the expansion of the neocortex. Researchers are increasingly realising, however, that the “little brain” or cerebellum also expanded during evolution and probably contributes to the capacities unique to humans. A Heidelberg research team has now generated comprehensive genetic maps of the development of cells in the cerebella of human, mouse and opossum. Comparisons of these maps reveal both ancestral and species-specific cellular and molecular characteristics of cerebellum development.