Nearly all organisms have a biological clock that keeps daily time. Biological clocks that drive near 24-hour rhythms in behavior and physiology have been found in a wide variety of organisms and cell types. The Herzog Lab studies the molecules, cells and circuits underlying these circadian rhythms in mammals using techniques that include planar electrode arrays, real-time cellular imaging and genetic manipulations (i.e. mutants, knockouts, transgenics, optogenetics, etc.). This approach is producing insight into the roles of specific neuropeptides and cell types in the rich repertoire of daily behaviors. We currently focus on circadian regulation in and by the suprachiasmatic nucleus (SCN) of the hypothalamus, the olfactory bulb (OB), and astroglial cells of the neocortex. We ask questions like: Which cells generate these rhythms? How do they synchronize to one another? What are the consequences when their rhythms are disrupted?