The breasts are made up of fat, connective tissue and glandular tissue. They have lobes where breast milk is made and ducts that connect the lobes to the nipple.
A woman's breasts are rarely the same size as each other, and may feel different at different times of the menstrual cycle, sometimes becoming lumpy just before a period.
Under the skin, an area of breast tissue extends into the armpit (axilla). The armpits also contain a collection of lymph nodes (lymph glands), which are part of the lymphatic system.
There are also lymph nodes just beside the breastbone and behind the collarbones.