  This article gives a brief qualitative description of the possible evolution
of the early Universe between the end of an inflationary epoch and the end of
Big Bang nucleosynthesis. After a general introduction, establishing the
minimum requirements cosmologists impose on this cosmic evolutionary phase,
namely, successful baryogenesis, the production of cosmic dark matter, and
successful light-element nucleosynthesis, a more detailed discussion on some
recent developments follows. This latter includes the physics of preheating,
the putative production of (alternative) dark matter, and the current status of
Big Bang nucleosynthesis.

Astrophysics;General Relativity and Quantum Cosmology;High Energy Physics - Phenomenology