Referring to the Tanner classification of pubertal development, the development of breasts can be divided into 5 stages. The stages of breast development in girls cannot be distinguished using age due to the large individual variability, and are generally graded according to breast development characteristics such as nipple diameter, areola size and breast morphology.1. Stage 1: Average age before 9 years old, nipple height below 3 mm, areola flat, and may have nipple invagination or convexity before puberty; 2. Stage 2: Average age 9.8 years old, nipple and areola diameter increases, the areola bulges toward the exterior of the breast, and the protruding areola can be palpated; 3. Stage 3: At an average age of 11.2 years, the nipple reaches an average diameter of 4 mm, the areola diameter increases, and the breast begins to bulge and is not confined to the interior of the areola; 4. Stage 4: At an average age of 12.1 years, the nipple, areola, and breast further increase in size, and the hallmark feature is that the nipple and areola bulge further, showing A secondary bulging demarcation line; 5. Stage 5: average age 14.6 years, nipple diameter is more than 7mm, the breasts in this period are developed and mature, and the shape is no different from adult women. There are individual differences in the development of breasts. In contemporary society, the richness of food and nutrition can easily cause girls to develop too early, for example, breast development occurs before the age of 9, or some endocrine diseases such as ovarian dysplasia, resulting in delayed breast development need to go to the hospital in time to clarify the cause, if necessary, the application of hormone therapy.