Female breast development is currently divided into three stages: the first stage is to 12 and a half years of age, this stage of mammary gland development is very slow; the second stage is from 12.515 years of age, at the latest 15 years of age, this is the fastest time of mammary gland development; the third stage of development is at the age of 18 years of age, the latest cut-off age of 18 years of age, when mammary gland development is basically complete. Therefore, the latest age of girls’ breast development is 18 years old, after 18 years old, women’s mammary glands basically stop developing, but with the beginning of sexual life and the beginning of breastfeeding will stimulate the mammary glands, but this stimulation and the normal development of two different concepts.