Based on presentations by world-renowned investigators at the 72nd annual Cold Spring Harbor Symposium on Quantitative Biology, this volume reviews the latest advances in biological clocks and rhythms. Topics include genetic and cellular studies aimed at characterizing circadian mechanisms; systems approaches to understanding physiological, endocrine, and neural networks; and models used for studying mental and physical cycles. A variety of normal and abnormal chronobiological patterns are discussed, including sleep, aging, migration, hibernation, seasonality, depression, and arrhythmias.