Generally, girls menstruate about 2 years after the development of the labia, but there are individual differences. Adolescent girls will usually be around 10 years old when the ovaries begin to develop and secretion of estrogen, the genitals begin to develop, including pubic mound bulging, labia major and minora development and pigmentation, and accompanied by the development of secondary sexual characteristics, such as breast eruption, pubic hair and armpit hair growth, and so on. Generally, girls will have menstruation about 2 years after the labia develop, but there will be individual differences. A girl’s first menstruation is the first menstrual period, which is an important sign of puberty, and mostly occurs between the ages of 13 and 14. However, due to the influence of genetic factors, nutrition and body weight, the age of the first menstruation may vary, but if there is no menstruation after the age of 16, it is necessary to go to the hospital in a timely manner in order to find out the cause, and under the guidance of the doctor to treat it positively.