When the breasts start to grow, this is normally the first sign of puberty that can be seen on the outside of a girl's body. This usually happens when girls are about the age of 10.5 years. 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 six to 12 months, both breasts will have started growing. The swelling can be felt and seen outside the edges of the areolae. About one and a half to two 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. Whether the breasts are small or large depends on how much fat there is in the body.