Lots of girls and guys worry about when their bodies will
develop. Guys wonder when their voices will get deeper, when
they'll need to shave, or when their penises will grow. Girls
want to know when their breasts will develop or when they'll get
their first period. If a friend or a younger brother or sister
develops first, they may worry that there's something wrong with
them. Different Variations of Normal The fact is that physical
development starts at different times and progresses at
different rates in different people. So, the beginning of the
development that comes with puberty varies from person to person
— and that's completely normal. The earliest physical change of
puberty for girls is usually breast development, which most
often begins around 10 or 11 years. But it's perfectly normal
for breast development to start anytime between the ages of 8
and 13. A girl's first menstrual period usually occurs about 2
to 21/2 years after breast development begins. Boys begin their
development on average around