Large nipples are primarily genetically related, but women who are breastfeeding can also have enlarged nipples due to sucking and tugging by their babies. Nipples are composed mainly of connective tissue and smooth muscle, and their size is usually determined congenitally and is genetically related. The nipple of an infertile woman is the size of a soybean and gradually protrudes as the breast develops and the areola matures. If the nipple becomes invaginated which may interfere with breastfeeding, intervention and, if necessary, surgical correction is required. After pregnancy, the areola protrudes due to estrogen stimulation, a Montserrat node that protrudes from the areola appears, and the nipple increases slightly in preparation for breastfeeding. Nipple enlargement can also occur during breastfeeding due to conditions such as breast-holding and sucking stimulation by the baby. The size of the nipple itself has no effect on the body, but if the nipple is too small or invaginated during breastfeeding, breastfeeding may be affected by difficulties in the baby’s articulation.