The cosmic microwave background is relic light that has been traveling since 400,000 years after the Big Bang. It was first detected in 1965 by Arno Penzias and Robert Wilson, providing strong evidence for the Big Bang scenario. The CMB gives us our earliest view of the Universe, and the tiny anisotropies in the light have since provided a great wealth of further information about the origins, contents, and evolution of our Universe. I will talk about its discovery, and the evolution of the field in the past decades using the COBE, WMAP, and Planck satellites together with a host of experiments from the ground and balloons. I will then discuss prospects for the next decade or more of CMB research, including the search for primordial gravitational waves.