Astronomical observations at near-infrared wavelengths offer unique opportunities for studying the universe. Important classes of low-temperature objects, such as the lowest-mass stars and brown dwarfs, as well as distant members of our own solar system, are readily detected in this wavelength regime. The penetrating power of infrared radiation for seeing through interstellar dust also permits views of the critical processes of star formation in galactic regions that are too dust-enshrouded for study at shorter wavelengths. Perhaps most important, near-infrared observations permit the detection of distant galaxies and supernovae, seen as they were in early epochs of cosmic time, because the expansion of the universe stretches their light – that was originally emitted at ultraviolet or visible wavelengths – red-shifting it to be detected as infrared radiation when it arrives at Earth.