The sleep-wake cycle is a physiological rhythm phenomenon prevalent in humans and higher animals. In humans, sleep can account for up to one-third of life, and is a physiological process essential for maintaining the health of the body and the normal function of the central nervous system. Normal sleep in adults is usually 7-9 hours, but time is not the only criterion for judging the quality of sleep. The regulation of the sleep and wake cycle is a physiological process involving the coordination and integration of multiple centers and systems, and the normal process includes the waking state and the sleeping state. The waking state is behaviorally characterized by a variety of changing motor activities and active thinking activities, and is very sensitive to environmental stimuli and can quickly make various adaptive responses. Sleep states can be divided into two states, namely non-rapid eye movement sleep (NREM) and rapid eye movement sleep (REM). Normal sleep starts with NREM, also known as slow-wave sleep. According to the depth of sleep and the degree of EEG slow wave NREM is further divided into four stages, sleep onset, light sleep, moderate sleep and deep sleep. the REM sleep stage is fast wave sleep, which alternates with NREM. Generally in one night will experience 4-6 NREM/REM cycles of 90-120 minutes each, with NREM getting shorter and REM getting longer. In summary, the normal sleep time for adults is roughly 7-9 hours, and it is not the case that the longer the time the better the sleep, nor is it the case that the shorter the time the worse the sleep. Healthy sleep helps eliminate fatigue, restore physical strength, defend against diseases, and also promotes human growth and development, improves intelligence and prolongs life span, healthy sleep is an important part of a good life.