Menarche, also known as menarche, refers to the first menstruation. Represents a girl's body and goes through puberty. Before menarche, girls' breasts have begun to develop and their height has suddenly increased. Some girls have grown pubic hair or armpit hair. Menstruation usually occurs two years after breast development. It is one of the important signs of puberty for girls to menstruate for the first time.

Menstruation represents the development of endometrium stimulated by estrogen, and also represents the opening of "pathway" from uterus to cervix to vagina. The age of menarche of most girls is 12- 16. Generally speaking, menarche is often anovulatory menstruation, and ovulation occurs after menarche 1 year.