Now let's move on to estrogen. So estrogen is initially released by the ovarian follicle, but when ovulation takes place, it's the corpus luteum that begins to release our estrogen. And finally, as the corpus luteum begins to break down, it's the placenta once again that takes over the role of releasing our estrogen. Now estrogen has many important functions during pregnancy, so its first important function is to actually generate the endometrium. But during pregnancy it serves three functions. It basically acts to actually enlarge our breasts of the woman, to basically prepare the woman for the process of lactation that takes place following birth.