Motivated by inflation, the theory of big-bang nucleosynthesis and the quest for a deeper understanding of the fundamental forces and particles, a very successful paradigm for the development of structure in the Universe has evolved. It holds that most of the matter exists in the form of slowly moving elementary particles left over from the earliest moments (cold dark matter or CDM) and that the small density inhomogeneities that seed structure formation arose from quantum fluctuations around $10^{-34}\sec$ after the bang. A flood of observations is now testing the cold dark matter paradigm -- from determinations of the Hubble constant to measurements of the anisotropy of the Cosmic Background Radiation (CBR) -- and could reveal the details of the theory as well.

15 pages, 9 Postscript figures