Staying up late will be detrimentl to human health, because the adrenal cortex hormone and growth hormone are all secreted during the night when people are sleeping. The former is secreted before down, which can promote the metabolism of carbohydrate in human body, and protect the development of muscle; while the latter is produced only after sleep, which can not only promote the growth and development of young people, but also can delay aging process of the elderly. As a result, staying up late will cause a variety of harms to human body. The most serious sequence caused by staying up late is fatigue and lack of energy. The immunity of human body will decrease accordingly. Consequently, some other symptoms such cold, gastrointestinal infections, allergies will also appear. The second consequence of staying up late is migraines. Sleep deprivation can trigger headache in the next day, and having a headache for a long period of time could read to migraines. Moreover, long-term staying up late will slowly cause some neurological and psychiatric symptoms such as insomnia, forgetfulness, irritability, and anxiety. The third harm of staying up late is dry skin, dark spots, and acne. The period between 11:00 pm to 3:00 am in the next day is the time for the meridians in human body to move to gall bladder and liver. If these two organs do not have adequate rest, it will be reflected on the skin. So some problems such as roughness, yellowish face, dark spots and acne will appear. To sum up, frequent fatigue and decreased immunity, migraines, and skin problems are the harms caused by staying up late. There also other harms, such as poor eyesight or dysfunction of the liver. These bad effects should be taken into consideration when people decide to stay up late for significant reasons