Puberty can start when you're 7 or not until you're 13, but it usually starts when you're 10. The process can take anywhere between 1½ –4 years. Generally, girls can expect their first period about 2 –3 years after the first signs of breast development. Here are some clues that will help determine when you will get your period and begin puberty: Heredity —ask your mother or other female relative how old she was when she had her first period. You'll probably get yours at the same age. (Note: Doctors have found that the age of puberty is about a year younger now than it was for your mother's age group.) Race —African-American girls usually show signs of puberty —a bit earlier than Caucasian girls. Weight —very thin girls begin to menstruate a bit later; heavier girls may begin early. Girls who develop earlier than most of their friends often feel "weird" or self-conscious. That's normal. But girls who develop later than most also feel strange —kind of left out of the club. Remember, eventually all girls get to be young women in their own time. Wondering when puberty starts? Get helpful information and advice at BeingGirl.com.