  We review the cosmological implications of the flat directions of the
Minimally Supersymmetric Standard Model (MSSM). We describe how field
condensates are created along the flat directions because of inflationary
fluctuations. The post-inflationary dynamical evolution of the field condensate
can charge up the condensate with B or L in a process known as Affleck-Dine
baryogenesis. Condensate fluctuations can give rise to both adiabatic and
isocurvature density perturbations and could be observable in future cosmic
microwave experiments. In many cases the condensate is however not the state of
lowest energy but fragments, with many interesting cosmological consequences.
Fragmentation is triggered by inflation-induced perturbations and the
condensate lumps will eventually form non-topological solitons, known as
Q-balls. Their properties depend on how supersymmetry breaking is transmitted
to the MSSM; if by gravity, then the Q-balls are semi-stable but long-lived and
can be the source of all the baryons and LSP dark matter; if by gauge
interactions, the Q-balls can be absolutely stable and form dark matter that
can be searched for directly. We also discuss some cosmological applications of
generic flat directions and Q-balls in the context of self-interacting dark
matter, inflatonic solitons and extra dimensions.
