This usually begins when girls are about 9. A lump that is a bit hard appears in each breast under the areola, which is the dark ring around the nipple. The lump in one breast may grow before the other one. This is called breast budding. Within 6-12 months, both breasts will have started growing. The swelling can be felt and seen outside the edges of the areolae. About 1 and a half to 2 years after the breasts first start growing, they are close to the shape and size of an adult woman's breasts. The nipple and areola may be on a smaller mound on each breast. This small mound usually goes away when each breast is fully grown. Breast size depends on the body's amount of fat.