The sleep-wake cycle is a physiological rhythm that is common in humans and higher animals. In humans, sleep can take up to one-third of the time of life and is an essential physiological process to maintain the health of the body and the normal function of the central nervous system. Healthy sleep helps to eliminate fatigue, restore physical strength, defend against diseases, and also promotes growth and development, improves intelligence and prolongs life expectancy. The length of sleep varies from person to person, generally speaking in adults, 7-9 hours of sleep a day is best, if occasionally less sleep at night, you can use the time at noon to make up for it, according to scientists research shows that adults who sleep 7-8 hours a night have a longer life expectancy, if more than 10 hours 80% may have disease conditions. Sleep but time is not the only criterion for judging the quality of sleep. The regulation of sleep and wake cycle is a physiological process involving multi-center and multi-system coordination and integration, 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. The sleep state can be divided into two states, namely non-rapid eye movement sleep (NREM) and rapid eye movement sleep (REM). Normal sleep starts with NREM, which is also known as slow-wave sleep with slow metabolism and decreased nerve cell activity. Depending on the depth of sleep and the degree of slow wave EEG NREM is subdivided into four stages, sleep onset, light sleep, moderate sleep and deep sleep. the REM sleep stage is fast wave sleep, alternating 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, adults sleep roughly 7-9 hours a day, and it is not the case that the longer the time the better the sleep, nor the shorter the time the worse the sleep. The sleep latency, number of sleep awakenings and total sleep time can be analyzed according to the EEG performance, eye movements and sleep depth during sleep.