You might not give your ovaries much thought (unless you’re trying to get pregnant), but even if you don’t think about them on the reg, these walnut-sized organs actually play a huge role in your every day life. “From a biological perspective, we’re put on the Earth to make more of us, so that kind of makes the ovaries one of our most important organs,” says Mary Jane Minkin, M.D., clinical professor of obstetrics, gynecology, and reproductive sciences at the Yale School of Medicine. Here are five things you didn’t know about your best reproductive friends.

1. They Produce a Whole Lot of Hormones

Your ovaries secrete estrogen and progesterone, says Minkin. These two hormones are responsible for the development of the female body during puberty (think boob growth, your period, and the widening of your hips). Estrogen and progesterone also prep the uterus for conception—and not producing enough can lead to trouble getting pregnant. Plus, your ovaries churn out your body’s supply of testosterone (albeit in smaller amounts than the estrogen), which you can thank for your sex drive. (Kick-start your new, healthy routine with Women’s Health’s 12-Week Head-to-Toe Transformation!)