Introduction From the Sun to Atoms — A Very Brief History of External Clocks As the World Turns Biological Clocks — Garden Variety Experiments Going to Extremes The Biological Clock's Mastermind Wrinkles in Time — Temperature-Circadian Interactions Oscillation Making Genetic Connections — What Mutant Flies Reveal Genomic Timing Ingenious Devices — Getting a Handle on Time Sleep — A Cycle in Time Out of Time — Let Sleeping Students Lie A Clinical Lesson in Circadian Rhythms Meet the Lecturers Exhibit Credits