Breast development in girls is influenced by the level of hormones in the body and usually begins to develop at the age of 9-11. There are also some girls with abnormal secondary sex characteristics that may have delayed breast development or premature breast development. I. Normal development: The development of nipples usually begins at the age of 9-10, the mammary glands begin to develop at the age of 10-11, and the fat in the breasts begins to develop at the age of 12-13. The developed breasts are spherical and located between the 3rd and 6th ribs. If the breasts develop normally, no special treatment is needed. Second, abnormal development: 1, delayed development: if more than 16 years old has not yet developed, you need to consider whether the development is delayed or ovarian dysplasia, pituitary dysplasia and other endocrine diseases, you need to go to the hospital in a timely manner to clarify the cause. If the ovaries are unable to secrete estrogen causing breast dysplasia, appropriate estrogen supplementation is required. If breast dysplasia is caused by genetic factors, there is usually no effective intervention method, if you are more concerned, you can consider plastic surgery in adulthood; 2. Premature development: If breast development occurs before the age of 8, it is considered precocious puberty, it is recommended to improve the pituitary MRI, sex hormone level, bone age, gynecological and breast ultrasound and other examinations as soon as possible to clarify the cause of premature breast development and remove the cause in time. If it is central precocious puberty, drug treatment can be applied. Avoid consuming or using nutrients and foods containing hormones in daily life. During breast development girls should pay attention to ensure a balanced diet and eat more foods rich in fat and protein such as beef, milk, shrimp, etc. Avoid excessive dieting that leads to severe fat loss in the body and breast dysplasia.