  The stellar initial mass function (IMF) is a fundamental astrophysical
quantity that impacts a wide range of astrophysical problems from heavy element
distribution to galactic evolution to planetary system formation. However, the
origin and universality of the IMF are hotly debated both observationally and
theoretically. I review recent observations of the IMF across a variety of
environments. These suggest the IMF is surprisingly invariant between
star-forming regions, star clusters, and spiral galaxies but that it may also
vary under extreme conditions, including within the Galactic center and early
type galaxies.
