Ticking away inside the human body are the timepieces that govern our daily and seasonal lives. This program shows how these biological clocks dictate physiological behavior—determining when our brains are most alert, when our stomachs are ready to break down food, and when our bodies want to sleep. Viewers learn why most babies are born in the early morning, why most teenagers want to sleep until noon, why most heart attacks occur between 8 and 10 am, and why most Olympic records are broken late in the day. Veteran chronobiologists, including Dr. Till Roenneberg of the University of Munich and Dr. Russell Foster of Imperial College, London, add their expertise to the program. A BBC/Science Channel Co-production. (49 minutes)