Girls usually start to grow breasts at the age of 8 to 12. It is a normal physiological phenomenon for girls to enter puberty around the age of 10, when their breasts start to develop. Girls start to grow breasts around the age of 8 to 12, which is also the period when the breasts start to develop normally. If the phenomenon of breasts nucleus and secondary sexual characteristics development occurs before the age of 8, it may be caused by precocious puberty, which should be taken seriously and go to the hospital in time to find out the cause, and then intervene and deal with it in a timely manner. During the period of breast growth, it is recommended to take preventive measures, pay attention to personal hygiene habits, do not use hands to squeeze, otherwise it will easily lead to inflammation of the mammary glands, parents should pay attention to the changes in the child’s body, and if there is any abnormality, take the child to the hospital as soon as possible for consultation and treatment.