Under the influence of sex hormones and other endocrine agents in the body, adolescent girls will begin to develop their breasts, which will appear as mild breast augmentation, nipple protrusion, areola enlargement, lumps, swelling and pain. 1. Mild breast augmentation: During puberty, girls’ breast buds start to grow, which can be manifested as obvious mound-shaped augmentation along with the gradual increase in the development process. 2. Nipple bulge: During pubertal development, the nipple of a girl’s breast is affected by estrogen and gradually bulges and grows with the progress of development. 3. Enlarged areola: During puberty, the areola of a girl’s breasts can be slowly enlarged by the influence of estrogen, and the color of the areola can be deepened to different degrees. 4. Lumps: during puberty the girl’s chest glandular hyperplasia can appear breast nucleus, usually in the nipple, areola can be touched under the peanut or bean size hard lump-like objects, there is a mild pain, this hard lump will gradually increase with age and become softer. 5. Pain and distension: puberty during the development of the girl’s chest will be distended and painful, especially in the time of menstruation, the pain is more intense, usually due to the large number of sex hormone secretion stimulation of the glands of the menstrual period, which leads to a large amount of pain. 6. This is usually due to the large amount of sex hormone secretion in the body during menstruation, which stimulates the glands. Girls chest development is generally 9-13 years old, chest development is mostly earlier than the first menstruation, with age, breasts, nipples, areola will continue to develop and increase, is a normal physiological phenomenon. When girls are developing breasts, they should pay attention to a balanced diet, avoid picky eating, eat fewer snacks, have a regular work and rest schedule, wear comfortable underwear, and keep their skin clean.