The discovery of X-rays was a boon to astronomers because it let them explore events in our universe in new ways. However, that's not all X-rays are good for. Before X-rays were discovered, the only way for a doctor to look into a patients body was to cut it open. However, this was very dangerous so most doctors tried to feel out the problem with their hands first, even though it wasn't an accurate technique. Because X-rays can penetrate skin (due to their small wavelength), they allow doctors to view bones and organs inside of your body. This can help diagnose everything from a broken arm to swollen lymph nodes. Besides, it's much less painful to have a doctor take a picture of your broken arm than to let him poke and prod it.