I'm 13 and have no boobs but my friends do. What can you do to make them grow?

I do understand your frustration, but you're still very young. Your breasts will continue to grow at least until age 18 after puberty and maturation. All the best.

That's a really common concern from girls your age.  Although I wish there was an easy solution, breast development occurs at different rates between individuals.  At this point - although it's frustrating - you just have to wait as your body develops naturally. You may have started to develop later than your friends, but rest assured that your breasts will continue to grow until late adolescence.Best, Stephanie Power MD, FRCSC