The Department Genes and Behavior investigates in the mouse the dynamic interplay between gene expression, development and behavior. Recently we developed efficient methods to detect, visualize, archive and mine spatial gene expression patterns in mammalian tissues at the mRNA level (www.genepaint.org). These data provide a powerful starting point to address genetic regulatory network. Research focusing on mammalian brain development attempts to establish hierarchies in signaling cascades while our chronobiology studies are directed at the discovery and elucidation of novel pathways by which genes control circadian behavior at an organismal level.