Remember Superman’s X-ray vision? His eyes shot X-rays at a door; the beams bored through, and he could see what his enemies were up to on the other side. Only doors made of lead could foil Superman. Lead is a good shield against X-rays. That’s why we wear heavy lead aprons at the dentist’s office. But Superman’s X-ray eyes came from the imagination of his creator. Eyes can’t shoot beams of light. Our eyes see when light from other sources, like the Sun, is reflected back from an object. However, X-rays are indeed a kind of light—a kind that is invisible to us. X-ray light has a lot more energy than visible light. That’s how it can penetrate wooden doors—or skin and muscle.