Under normal circumstances, girls’ breast development usually takes place between 8 and 12 years old, but there are some individual differences that need to be analyzed on a case-by-case basis. Usually, the first development of the breast occurs when girls are about 8-9 years old, mainly manifested by the gradual expansion of the breast, such as a small mound, while the areola area expands, the nipple and areola area will appear hard nucleus, most girls will complain of pain in their breast area, especially after pressure is more obvious. The real breast development is mainly after the onset of menstruation, and around 12-13 years old the appearance of the breast begins to gradually produce changes, gradually augmentation, until 15-16 years old can gradually develop to adult breast appearance, and 80% of girls to 16-19 years old breast development close to adult. During breast development, women need to pay attention to a balanced diet, develop good habits, eat more protein and vitamin-rich foods to help promote breast development, and avoid repeatedly squeezing and kneading their breasts as much as possible.