Before girls reach puberty, as secondary sexual characteristics develop, the ovaries begin to secrete estrogen and progesterone, leading to breast development, growth of pubic and axillary hair, and the development of internal and external genitalia with vaginal discharge. The first menstruation usually occurs 1-2 years after these conditions, mostly around the age of 13, some earlier and some later. If menstruation occurs before the age of 10, it is considered precocious, and if it does not occur after the age of 16, it is considered delayed and the cause needs to be identified. In these cases, it is recommended to check the sex hormones, ultrasound, bone age, etc. Precocious puberty needs to be treated and not to eat foods rich in hormones, such as fruits and vegetables that are out of season, artificially farmed chicken, duck and fish, and avoid foods such as royal jelly and soy milk. For those who do not have menstruation, chromosome examination is also needed to rule out Turner syndrome, chromosomal abnormalities, etc.