Each month inside your ovaries, a group of eggs starts to grow in small, fluid-filled sacs called follicles. Eventually, one of the eggs erupts from the follicle (ovulation). It usually happens about 2 weeks before your next period.
After the egg leaves the follicle, the follicle develops into something called the corpus luteum. The corpus luteum releases a hormone that helps thicken the lining of your uterus, getting it ready for the egg.
The Egg Travels to the Fallopian Tube
After the egg is released, it moves into the Fallopian tube. It stays there for about 24 hours, waiting for a single sperm to fertilize it. All this happens, on average, about 2 weeks after your last period.