I. INTRODUCTION The paradigm of primordial inflation has met with glorious successes over the past three decades since its conception [1–6] (for some excellent reviews on inflation, see [7–11]). In the most general scenario, inflation occurs because a slowly rolling scalar field, the inflaton, dynamically gives rise to an epoch of accelerated expansion dominated by a false vacuum (for a review on inflaton models, see [10]). During inflation, quantum fluctuations imprinted on space-time are stretched outside the Hubble patch. These primordial fluctuations even- tually re-enter the Hubble patch, whence their form can be extracted by observing the perturbations in the Cosmic Microwave Background (CMB) radiation. Slow-roll inflation- ary scenarios generically predict almost Gaussian adiabatic perturbations with a nearly flat spectrum (for a review on generating quantum fluctuations during inflation, see [12]), which have met with an unprecedented success with the latest observations, see the recent data from WMAP [13] $^{1}$. Future CMB experiments such as PLANCK 2 will improve the current data, and also provide useful constraints on the scale of inflation in terms of primordial gravity waves [14–17], departure from random Gaussian fluctuations [18–23], isocurvature perturbations [24, 25], etc. The end of inflation can be considered as a paradigm for the origin of matter, since all mat- ter arises from the vacuum energy stored in the inflaton field. However the present models do not give clear predictions as to what sort of matter there is to be found in the early universe. Theoretical and observational successes of the Big Bang Nucleosynthesis (BBN) have con- strained the degrees of freedom around the temperature of T ≥ 1 − 5 MeV, which contains the Standard Model (SM) quarks and leptons and three generations of neutrinos [26–29]. The present observational uncertainties allow only one extra species of relativistic particle at the time of BBN [28, 30]. From the current observations we also know that SM baryons constitute about 4.6% of the total energy density, almost 23% of the total energy density is in non-luminous, non-baryonic dark matter, and the rest of the energy density is in the form of dark energy [13]. Besides the cosmological issues, one of the theoretical challenges is to understand why the mass scale of the SM, of O (100) GeV, is much lower than the scale of gravity, M$_{P}$ = 1 See http://map.gsfc.nasa.gov/ . 2 See http://www.sciops.esa.int/index.php?project=PLANCK&page=index 8