Sleep problems and depressed mood often go hand in hand, forming a frustrating cycle. Michael Terman, PhD, has devoted his career to studying the brain functions that feed these disorders. His discoveries in chronotherapy have been widely recognized as game-changers by the medical establishment, and his 2010 New York Times op-ed, “Sleeping (or Not) by the Wrong Clock,” shot to number one on the paper’s list of most-forwarded online articles. In Chronotherapy, Terman and McMahan reveal the heart of his findings, a powerful program that recalibrates our internal clocks—our exquisitely designed, natural sensitivity to the timing and brightness of light exposure. These delicate mechanisms are often decimated by the modern demands of a 24/7 lifestyle. Beginning with a questionnaire that pinpoints the problem areas, Terman helps readers decipher when their natural internal night begins and ends. The treatment process can then start, incorporating the power of natural light and, when necessary, supplemental light therapy. His approach has brought relief to thousands of sleep sufferers, as well as those burdened by bipolar disorder, seasonal affective disorder, depression, sleep disorders due to around-the-clock work schedules, and other impediments to vibrant health. For the first time, his findings are now available for a general audience, sharing the essential elements of chronobiology in clear, authoritative, scientifically grounded chapters that are easy to apply to a variety of situations.