Abstract
Most organisms have evolved an internal clock to predict daily recurring events. This clock with a period of about 24 hours, termed circadian clock, allows organisms to organize biochemical and physiological processes over one day. Changes in lighting conditions as they occur naturally over seasons or man-made by jet lag or shift work, change sleep phase in order to synchronize an organism’s physiology to the environment. A misalignment results in sleep disturbance and mood disorders. Here we discuss how we study various body clocks in mice to understand their synchronization avoiding development of disease.