The development of breasts in girls before the age of 8 is usually called precocious puberty. Precocious puberty can be defined according to the age of development and physical signs. 1. Age: Breasts begin to develop before the age of 8 in girls, menstruation before the age of 10, and in some boys, too, is called precocious puberty. In addition to the improvement of living standards, the appearance of the breasts of obese children can be enlarged, the breasts are mostly accumulated fat, not breast development. 2. Physical signs: may be related to the living environment, diet. It leads to the increase of armpit hair, the growth of height and the first menstrual period in the late stage. It can also cause hyperpigmentation of the external genitalia, secretions and changes in pubic hair. Once the child is found to have the manifestation of precocious puberty, it is recommended to go to the hospital in time, follow the doctor’s guidance, timely intervention and treatment.