The breast is mostly made up of fatty tissue. Within this tissue is a network of lobes, which are made up of small, tube-like structures called lobules, which contain milk glands. Tiny ducts connect the glands, lobules and lobes, and carry milk from the lobes to the nipple, which is located in the middle of the areola—the darker area that surrounds the nipple.
Blood and lymph vessels also run throughout the breast. Blood nourishes the cells, while the lymphatic system drains bodily waste products. The lymph vessels connect to lymph nodes, which are tiny, bean-shaped organs that help fight infection.