We are all painfully aware of our internal clock when we travel across time zones or undertake shift work. But our clocks also control our blood pressure and fat metabolism, as well as our cognitive abilities. In many animals circadian clocks are responsible for behaviors ranging from courtship to insect pollinators. Plants even grow with daily rhythms and use their clocks to decide the correct seasons to flower. Join UCSD Professor and Dean of Biological Sciences Steve Kay and explore how these clocks are constructed, how they differ, and how systems biology may allow us ultimately to manipulate them to benefit health and agriculture.