There are several precursors to girls’ menarche: 1. The development of the first sex characteristics will occur when girls are about 12 years old, usually the development of the external genitalia, gradually approaching the adult level. 2. With the growth of puberty, girls will also have the development of the second sex characteristics, firstly, when the second sex characteristics appear, girls’ breasts will develop and grow, and secondly, the voice tone will be relatively high. 3. Girls will have armpit hair, pubic hair growth, so when this happens, it generally indicates the first menstruation, in addition, after the development of girls’ breasts, about 2-3 years will have the first menstruation. In addition, some girls will have increased vaginal discharge or stretched leucorrhea, which are all signs of the first menstruation.