Prior to puberty, the structure of the breast tissues is exactly the same in both females and males. Once a girl reaches puberty, her ovaries start to produce high amounts of the female sex hormones - estrogen and progesterone. These have direct relevance with the growth and development of a girl's breast tissues.
In the structure of a fully developed breast, there are approximately 20 groups of lobes. These are glands that take care of producing milk at the time of pregnancy. Each lobule is in fact, an individual milk producing zone having a small tube leading from it called a ductile. The ductile links up to a wider tube called the ducts, which eventually open on to the surface of the nipples. Overall, the nipples will have about 20 of these duct openings which will activate during pregnancy.
In between the lobules, there is a mixture of fatty tissue and tough supporting tissues. This maintains the shape of the breast as there are no muscles or bones making up the structure of the breast. The supporting tissues link up to the muscles of the chest wall underneath.
On the outer surface of the breasts one can find the nipple surrounded by a darker skin called the areola. The color of the areola can differ from one woman to another. It can range from dark shades of browns to a bright fleshy pink. The areola can also differ in size which can range from being extremely small and may not be readily visible or it could even spread to a wide area around the nipple.