The developmental period usually refers to the age of puberty, when the breasts gradually become fuller, larger, and so on. For pubertal breast development, it usually takes about 4 years. At this time, adolescents begin to develop breasts due to the increased secretion of gonadotropins from the hypothalamus and pituitary gland, which leads to the development of the ovaries and a gradual increase in the secretion of sex hormones. When the breast fat, connective tissue proliferation, it will gradually full, bulging, and nipple, areola enlargement, but also accompanied by pigmentation phenomenon. In addition, adolescent children’s breasts are susceptible to the influence of estrogen and progesterone and menstrual cycle changes. The main manifestation of the pre-menstrual period of the mammary glands were hyperplastic changes, the breasts are slightly enlarged, mostly accompanied by a slight pain or tenderness. With the end of menstruation, the body’s hormone levels return to normal, and the symptoms of breast discomfort can be relieved on their own. During puberty, parents should choose the right underwear for their children, and should also establish the correct concept of growth and development to avoid children with low self-esteem. Daily attention to strengthen the chest care, avoid foreign body friction stimulation.