Precocious puberty is diagnosed when a girl develops secondary sexual characteristics before the age of 8 or has the first menstruation before the age of 10. The first clinical manifestation of girls is breast development, with nucleus formation and localized elevation into small mounds, while nipples and areolas gradually increase in size. The internal and external genitalia are enlarged, pigmentation of the labia minora, white vaginal discharge, redistribution of subcutaneous fat, early age of menarche, and possibly ovulation of menstruation. Most of the pubic hair appears about a year after breast development, while the axillary hair appears even later, often after menarche. Height often temporarily exceeds that of children of the same age. However, due to the further increase of estrogen level, the epiphysis closes earlier, so the time of height growth in children with true idiopathic precocious puberty is shortened, which affects the height in adulthood and causes short stature. The above developmental process is continuous and progressive until the final sexual maturity and fertility is achieved, but the speed of the process varies from person to person. In true precocious puberty, both male and female, the bone age is often significantly higher than the actual age, and thus the epiphysis matures too quickly and heals early, which will eventually affect the lifelong height of adults. Therefore, once the child is found to have early development, it is important to seek timely medical attention.