While experts still don't have all the answers, one fact they do know for certain is that sleep is not only important, it is essential to life! Physical, mental, and emotional health are all impacted by sleep. The world of sleep is filled with many unanswered questions and mysteries. While the exact physiological roles of sleep are still uncertain, researchers are confident that the body does a lot of valuable work while sleeping.

What is sleep? -- Riding the sleep cycle -- The four stages of sleep -- What happens to our bodies during sleep? -- Is sleep important? -- How long do people need to sleep? -- Sleep hygiene -- Dreams, dreams, dreams -- Sleep disorders -- Weird sleep! -- The bed -- How do animals sleep?