Endometriosis is a painful and often misunderstood condition where tissue similar to the lining inside the uterus grows outside of it—most commonly around the ovaries, fallopian tubes, and pelvic lining. This misplaced tissue behaves like normal endometrial tissue, thickening and breaking down with each menstrual cycle, but it has no way to exit the body, leading to inflammation, cysts, and scarring.