This work is an update of trigeminal research of the 1980s and 1990s. The authors are known neurocytologists for brainstem and cerebellar structures, and here they bring together their knowledge and focus on the trigeminal system. They present findings on the normal structure of trigeminal nuclei and trigeminal pathways, schematic drawings of serial sections, and a series of data that relate animal experiments to the human trigeminal system.