Breasts differ widely from one individual to another. Size, form, and colour are all hereditary characteristics. But on the contrary, breasts also vary and grow over the course of a woman's life.
A woman's breasts are glandular tissue (which produces milk) and fatty tissue (which creates fat). The breasts fully grow during pregnancy, and the development is aided by a complicated combination of hormones, including estrogens, progesterone, and prolactin. The breast size is determined by the quantity of fat in the breast.
