Sleep disorders are a group of medical conditions that impair the ability to sleep well on a regular basis. Some common signs and symptoms of sleep disorders are irregular sleep and wake cycle, breathing in an unusual pattern, and falling asleep at inappropriate times. Insomnia is a common type of sleeping disorder that can be caused by stress and anxiety, jet lag, hormones, or digestive problems. Polysomnography (PSG), electroencephalogram (EEG), and multiple sleep latency test (MSLT) are used to diagnose sleep disorders. The treatments for sleep disorders include medications such as sleeping pills and melatonin supplements, breathing device and surgery. Cognitive behavioral therapy or relaxation techniques can also help to reduce anxiety about getting enough sleep. This book outlines the basic science and clinical aspects of sleep disorders. A number of latest researches have been included to keep the readers up-to-date with the global concepts in sleep medicine. This book aims to serve as a resource guide for students and experts alike and contribute to the growth of the discipline.