  The advent of the Spitzer Space Telescope has revolutionized our
understanding of the history of star formation and galaxy mass assembly in the
Universe. The tremendous leap in sensitivity from previous mid-to-far IR
missions has allowed Spitzer to perform deeper, and wider, surveys than
previously possible at these wavelengths. In this brief review I highlight some
of the key results to come out of these surveys, and the implications these
have for current models of galaxy formation and evolution.
