Deep sleep is part of the entire sleep cycle, accounting for approximately 1/4 of all sleep time, which is equivalent to 2-3 hours. Clinical studies have shown that only with deep sleep can humans get sufficient rest, eliminate fatigue, strengthen immunity and regain strength. Measuring a person’s sleep should not be judged by the duration of sleep alone, but by the quality of sleep. If after waking up, one feels good about oneself, one’s body fatigue disappears, one is energetic, one is efficient in study and work, and one’s mind can stay awake, one has achieved the effect of deep sleep. Even if you only slept for 5 or 6 hours, the quality of sleep will be better if the time of deep sleep is guaranteed. On the contrary, even if you have slept for more than 10 hours, but still feel unclear, fatigue and low efficiency after waking up, it does not mean that your sleep quality is good. Lack of sleep can lead to a variety of diseases, make the body’s immune function decline, affect the clarity of brain thinking and response sensitivity, and affect the growth and development of adolescents, therefore, the importance of sleep quality should be highly valued.