Female breasts usually start to develop around the age of 10 to 11, but there are individual differences. Most female breasts begin to develop during puberty, which is around 10~11 years old, but there are some girls who develop earlier, around 9 years old may begin breast development, or some girls develop later, may start to develop at the age of 13~14 years old. It is not normal for girls to develop breasts too early or too late. If they develop too early, it may be due to early maturity. However, if the development is too late and the breasts are still not developed by the age of 18, it may be caused by diseases. Female breast development too early and too late is abnormal, must be timely to the hospital.