Work in my laboratory focuses on understanding the molecular basis of circadian clocks, which are innate biological clocks that control daily rhythms in physiology, metabolism and behavior. Essentially all organisms from bacteria to humans use circadian clocks to anticipate daily changes in environmental cues such as light and temperature, thereby conferring survival and reproductive advantages. The medical community, as well as the general public, has become increasingly aware of the importance of circadian clocks for human health, safety, performance and productivity. Numerous health problems, including some forms of depression as well as many sleep, neurological, cardiovascular and endocrine disorders, are associated with a dysfunctional circadian clock. My lab uses a simple model organism, the fruit fly Drosophila melanogaster, to determine how circadian clocks keep time and control physiological, metabolic and behavioral rhythms. The identification and characterization of clock genes in Drosophila revealed that circadian timekeeping is based on transcriptional feedback loops. Since core components of these feedback loops have been conserved between Drosophila and mammals, what we learn about the Drosophila clock should continue to be relevant to circadian clock mechanisms in mammals, including humans.