ANDY'S ANSWER: I'll bet your breasts have started started growing, but you just haven't really noticed yet. The first sign of puberty in girls is that the nipple parts of your breasts start to swell a little bit. This is called "breast budding" (Kind of like how a flower bud starts out.) Breast budding signals the start of puberty and the beginning of the changes that are going to happen to your body. If it hasn't happened to you yet, it doesn't mean anything is wrong. Every person developes depending on their own genetics.