It takes about 2~2.5 years for a girl’s breasts to begin to develop until the onset of menstruation, but the exact time cannot be determined due to individual differences. Puberty is the period from the beginning of the appearance of female secondary sexual characteristics to the development of maturity, generally breast development occurs at the beginning of puberty, female menstruation marks the maturity of the development of its reproductive function, so generally women in the breast development of 2 ~ 2.5 years after the onset of menstruation, but due to the role of genetics, the environment and other factors, the specific time for each individual can not yet be determined. For women, during puberty, the pressure of learning is relatively large, and at the same time, psychological sensitivity, it is recommended that they pay attention to rest, to ensure adequate sleep, appropriate relaxation, to maintain a happy mood, after menstruation, pay attention to the cleanliness and hygiene of the vulva, and diligently change the sanitary products. If a woman does not have breast development or menstruation at the age of 16, it is recommended to go to the gynecology department of a regular hospital for a complete examination of sex hormones and other related tests to determine the cause of the disease and then actively treat it under the guidance of the doctor.