How do you know when your breast is growing?

ANDY'S ANSWER: When a girl is starting puberty, the first thing that normally happens is called "breast budding" It's just a little swelling under the nipple that makes just the tips stick out a bit. This can start to happen as early as age 8. Some girls will notice the brown part of their breasts (called the areola) getting a little darker. Another sign that your breasts have started to grow is that they might be getting tender. I should mention that it is not unusual for one breast to start growing before the other one does, or one grows faster than the other one.