The breast changes with hormonal stimulation and age. At birth there is little breast tissue present. Breast development really starts during puberty and the normal development of breast structure is dependent on a normal balance of hormonal stimulation.
Breasts and nipple shape vary significantly. For example, it may be quite normal for a woman to have inverted nipples.
The majority of women have one breast slightly larger than the other.
With time the shape of a woman’s breasts change. The amount of breast tissue decreases and it is replaced with fat. The breasts are subject to the regular monthly hormonal cycle. For example, women often have more breast tenderness just before their periods. Hormonal replacement therapy may stimulate some new breast development.