  We review the particle theory origin of inflation and curvaton mechanisms for
generating large scale structures and the observed temperature anisotropy in
the cosmic microwave background (CMB) radiation. Since inflaton or curvaton
energy density creates all matter, it is important to understand the process of
reheating and preheating into the relevant degrees of freedom required for the
success of Big Bang Nucleosynthesis. We discuss two distinct classes of models,
one where inflaton and curvaton belong to the hidden sector, which are coupled
to the Standard Model gauge sector very weakly. There is another class of
models of inflaton and curvaton, which are embedded within Minimal
Supersymmetric Standard Model (MSSM) gauge group and beyond, and whose origins
lie within gauge invariant combinations of supersymmetric quarks and leptons.
Their masses and couplings are all well motivated from low energy physics,
therefore such models provide us with a unique opportunity that they can be
verified/falsified by the CMB data and also by the future collider and
non-collider based experiments. We then briefly discuss stringy origin of
inflation, alternative cosmological scenarios, and bouncing universes.
