When cosmologists map the universe, they are imaging its past. Our measurements of the cosmic microwave background fluctuations map the universe’s condition only a few hundred thousand years after the big bang. These maps reveal a universe that is both remarkably simple and very strange. The nature of the dark matter and dark energy that comprise 95% of the universe is one of the great mysteries of science and point to the need for physics beyond the standard model of astrophysics. Ongoing experiments in Chile and the South Pole are making higher resolution maps of the microwave sky. These maps reveal how the subsequent evolution of the universe has distorted the primordial image. These distortions let us trace the large scale distribution of mass, pressure, and momentum in the universe.