Children occasionally late to bed, generally no serious harm, but if a long time late to bed, may affect the development of height, resulting in poor concentration affect learning, serious may also lead to precocious puberty and so on. 1. affect height: promote the development of small children’s height growth hormone, is in the small children deep sleep secretion, small children often late to bed will affect the secretion of growth hormone, and ultimately may affect the development of small children’s height. 2. Impact on learning: sleeping late will make the brain can not fully rest, during the day, small children are prone to become inattentive, weak memory, weak reaction ability, etc., often late to sleep may have a serious impact on small children’s academic performance. 3. Precocious puberty: There is a melatonin in the human body that can restrain the release of pituitary gonadotropins to avoid precocious puberty. Often late to bed so that children exposed to artificial light source the longer the time, the melatonin produced by the body of the lower levels, it is easy to lead to precocious puberty. There are many other hazards of children sleeping late for a long time. Parents are advised to help their children develop the habit of going to bed early and waking up early when they are young in order to ensure the normal growth and development of small children. If there is any abnormality, consult a doctor in time.