In general, most women’s breasts stop developing at the age of 18-20, but a few women’s breasts can continue to develop until the age of 25, and some women can experience secondary development. The development of breasts starts after puberty, but the specific development status needs to take into account genetic factors, and there are individual differences and differences in the early and late development of breasts. Most women start to develop their breasts between the ages of 9 and 12, and they may experience breast swelling and areola enlargement; after the age of 18, the breasts mature and stop developing around the age of 20, and the breasts begin to set. In addition, some women may experience hormonal disorders, such as excessive secretion of estrogen or an imbalance in the ratio of estrogen to androgen, which may cause secondary breast development. During the breast development period, women are recommended to take part in physical exercise and increase nutrition, and can supplement protein-rich foods, such as milk, eggs, meat and fish, etc. They can also do more breast expansion exercises in general.