Most men start puberty at the age of 8-11, when the penis grows, enlarges and thickens under the function of the hypothalamic-pituitary-gonadal axis, which is a normal physiological process, except that some appear early and some appear late. Children who develop late sometimes formally enter puberty after the age of 16-17, but eventually they can basically develop to a level similar to that of other people. Therefore, there is no need to do special penis exercises, as long as you pay attention to nutrition, physical exercise, work and rest, avoid overwork, malnutrition, partiality, emotional stress, anxiety, etc. Many people with delayed development will have chronic diseases such as congenital heart disease, cirrhosis, uremia, anemia, diabetes, chronic diarrhea, severe malnutrition, endocrine metabolic disorders, etc. They need to be examined at a hospital to find out the cause.