The uterus is mostly composed of muscle. However, the inside lining of the uterus is made of "fluffy" endometrial tissue that grows and shrinks during the menstrual cycle. If a woman does not become pregnant, this lining sheds, causing a menstrual period. After a period, the lining grows rapidly under the influence of hormones like estrogen. Polyps are areas that grow a little too much. As they grow, they usually fan out but remain attached to a small stalk, kind of similar to a bush or a tree. The stalk is like the trunk of a tree, while the larger part of the polyp is like the branches (see photo below). They are usually about the size of a pencil eraser, although they can be even smaller. Rarely, polyps can grow to the size of an orange! - See more at: http://www.obgyn.net/laparoscopy/endometrial-polyps#sthash.2zaNmolN.dpuf