Research in the Smithsonian Astrophysical Observatory Optical and Infrared Astronomy Division spans extragalactic and galactic astronomy, with emphases on cosmology, the large-scale structure of the universe, cosmic gamma-ray sources, clusters of galaxies, clusters of stars, the halo of our galaxy, and the formation and evolution of stars and galaxies. Observations are made from orbiting observatories including the Hubble Space Telescope and the Spitzer Space Telescope, as well as from ground-based observatories such as the Multiple Mirror Telescope (MMT), Magellan, and Fred Lawrence Whipple Observatory (FLWO).