Predicted in the late 1940s, and discovered accidentally in the 1960s, the Cosmic Microwave Background (CMB) is a cornerstone of the edifice of modern cosmology. We review its discovery and then prese...Predicted in the late 1940s, and discovered accidentally in the 1960s, the Cosmic Microwave Background (CMB) is a cornerstone of the edifice of modern cosmology. We review its discovery and then present the "surface of last scattering"; the thin shell around us, at a distance now of about 46 billion light years, where most of the CMB photons we see today last interacted with matter. We discuss its high degree of isotropy, reflecting the high degree of homogeneity in the early universe.
