When used alone, X-rays are great for seeing the body's skeletal structure, but they're not necessarily very good for seeing internal organs. However, when X-rays are combined with a dye in a process known as fluoroscopy, the internal organs become visible.
Hysterosalpingography is a process by which a liquid contrast material is injected into the uterus through a catheter, allowing doctors to view much of a woman's reproductive system. Because the contrast material lights up when pulsed or beamed with X-rays, doctors are able to look for abnormalities in the uterus (like fibroids) and can examine the fallopian tubes for signs of blockages or closures. It's an effective, yet minimally invasive, way to help diagnose potential infertility issues.