During puberty, sexual development occurs in a set sequence. However, when the changes begin and how quickly they occur vary from person to person.
For girls, puberty begins around age 8 to 13 years and lasts about 4 years.
For boys, puberty begins around age 10 to 14 years and lasts about 3 years.
The chart shows a typical sequence and normal range of development for the milestones of sexual development.