  We present results from an on-going Hubble Space Telescope (HST) survey of a
large sample of ULIRGs (Ultra-Luminous IR Galaxies). New ground-based
observations are now being used to complement the HST data and to assist in the
interpretation of these complex objects. A rich spectroscopic, morphological,
and dynamical diversity is found within the ULIRG population, nearly 100% of
which are merger and/or collision remnants. The consequences of this diversity
may apply to the interpretation of distant submm/FIR sources and their
subsequent evolution.
