We spend a third of our lives sleeping, but how much do we really know about sleep? What kind of sleep is healthy? Sleep is a continuous process. If you wake up frequently or have difficulty maintaining a long period of time during sleep, something may be wrong as well. There are two forms of sleep, sleep without dreaming and sleep with dreaming. Non-dreaming and dreaming sleep alternate during the night, and the alternation is called a sleep cycle, which lasts about 90 minutes for adults and 60 minutes for children. A night’s sleep takes about four to five cycles to complete. The need for sleep varies from age to age, and children may sleep for more than ten or even twenty hours, except for milk. As they get older and reach adulthood, the amount of sleep continues to shorten, and for most people about six to eight hours is enough. Some people sleep for a long time, lie down and fall asleep, and still want to sleep after waking up, indicating that its sleep quality is poor and needs to be extended to supplement, such sleep is also not healthy. To measure whether the sleep is healthy, on the one hand, we have to see whether the sleep cycle is very reasonable, and on the other hand, we have to see whether the ratio of deep sleep and dreaming sleep is appropriate. If the ratio of deep sleep is too little and light sleep is too long, it means that the quality of sleep is also bad. What is the role of sleep? For children, adequate sleep ensures their intellectual development and physical development. During deep sleep, a large amount of hormones are released that will make this child grow. If the child has a short deep sleep, less hormones are released, so the child will not grow taller. And dreaming sleep is also a very important stage to promote the child’s intellectual development. Now children from elementary school to school, secondary school extracurricular homework is very much, learning pressure is also very high, in order to cope with the examination, in fact, a considerable part of children sleep is not enough, these sleep-deprived children use their own sleep time, with shortened sleep time to extend the study time. If you look closely, you will find that although the study time is extended, the efficiency is reduced because of the lack of sleep. In fact, if you can ensure that you get enough sleep, it will help you to study, and it is possible to properly improve the efficiency of learning. For us adults, sleep is of course very important. In addition to our body’s normal metabolic and endocrine function, for our daily activities, we sleep is a very good rest. On the one hand, sleep without dreaming is very important for the rest of our physical activities, and sleep with dreaming is very relevant to the rest of our mental activities, especially to the formation of our new memory and the strengthening of memory. A person who is tired enough to move house today, may sleep at night with a prolonged proportion of deep sleep. If it is said that he always do some brain activity during the day, or copywriting work, then work to do more, overuse of the brain, sleep at night, may be dreaming about doing this. In fact, as far as dreaming is concerned, such a sleep process is a very important process. These two forms of functions are very useful for us, for our daily life, for our physiology. Also for the elderly, both types of sleep are very important. Their deep sleep time and dreaming time are relatively shorter, their sleep quality is poorer, and they are more likely to be woken up, so we have to provide a more comfortable and quiet environment for the elderly to ensure his sleep.