Technically speaking, puberty is nature's way of transforming a child into an adult, all for the sake of reproduction. While both girls and boys go through puberty, girls reach puberty and sexual maturity at earlier ages than boys do. Starting at around age 9, girls begin to gain about 17% to 18% of their adult height.
Puberty Breast DevelopmentBreast development is an early sign of puberty in girls. This can happen before age 9 in some girls, but later in others.