It is very attractive to theorize that at some early time the universe grew very rapidly, i.e. an inflationary epoch . At the end of the expansion the universe reheats to a very high temperature, which is required for nucleosynthesis.
Further evolution proceeds as in the standard big bang theory.
Inhomogeneities inside a hubble sphere are causally connected and inhomogeneities easily smoothed out. Inflation also provides a natural mechanism for structure formation through quantum fluctuations which are important during the inflationary epoch. In this supercooled state, the field dominates the energy density and drives inflation until the universe can undergo a first order phase transition . See my classmate Chet's Inflation Page for more. This indicates that supersymmetry occurs at the GUT time scale.