Although sleep consumes one-third of our lives and is a common feature among all animals, how the brain orchestrates sleep remains largely unexplained. To fill in this knowledge gap, Geoffrey Goodhill, PhD, professor of developmental biology and of neuroscience at Washington University School of Medicine in St. Louis, and colleagues will track each cell in the brain as it cycles between waking and sleep states. The goal is to identify the fundamental principles governing sleep at the whole-brain scale and how they are disrupted in sleep disorders.