Most objects in the universe radiate light at wavelengths ("colors") well beyond the limits of human vision. This radiation provides sometimes complementary, sometimes unique information on the physical nature of the radiating objects. Radio astronomers study light with the longest wavelengths. In this talk I describe the physical phenomena that radio astronomers observe, and give a brief tour of the Radio Universe, from solar Coronal Mass Ejections, to interacting galaxies, to the Cosmic Microwave Background.