We're designed to spend a full third of our lives asleep, yet sleep is increasingly becoming a luxury in busy, modern life. While our bodies insist on sleep - without it we die -, statistics show that insomnia is rampant, and consumes billions in medical bills worldwide. This definitive, illustrated reference guide, written by one of science's most eminent sleep experts, offers an accessible understanding of the science behind sleep. It explains the elements of the sleep state, details the physical functions that aid and challenge a restful night, examines our developing relationship with sleep throughout our lifetimes, and explores sleep disorders and how to remedy them. Use this detailed guide to assess your own personal relationship with sleep, and craft your own approach to having a full night's sleep with maximum physical return.