Puberty begins around 10-14 years in girls and one or two years in boys
In girls, the first sign of puberty is the beginning of breast development the growth of pubic hair typically begins next, followed by the growth of hair in the armpits. A minority of girls, however, begin to develop pubic hair prior to breast development.
The onset of menstruation (having periods) usually happens later than the other physical changes and usually occurs around two and a half years after the onset of puberty.