  During Big Bang Nucleosynthesis (BBN), in the first 20 minutes of the
evolution of the Universe, the light nuclides, D, 3He, 4He, and 7Li were
synthesized in astrophysically interesting abundances. The Cosmic Microwave
Background Radiation (CMB) observed at present was last scattered some 400
thousand years later. BBN and the CMB (supplemented by more recent Large Scale
Structure data), provide complementary probes of the early evolution of the
Universe and enable constraints on the high temperature/energy physical
processes in it. In this overview the predictions and observations of two
physical quantities, the baryon density parameter and the expansion rate
parameter, are compared to see if there is agreement between theory and
observation at these two widely separated epochs. After answering this question
in the affirmative, the consequences of this concordance for physics beyond the
standard models of particle physics and cosmology is discussed.
