Cosmological inflation is currently considered to be the best paradigm for describing the early stages of the universe. The inflationary epoch magnifies the tiny quantum fluctuations present at the beginning of the epoch into classical perturbations that l eave an imprint as anisotropies in the cosmic microwave background (CMB). It has recently been realised that the predictions of inflation for the spectrum of perturbations may not be robust against trans-Planckian (string) physics. Recently, using WMAP, the CMB anisotropies have been measured accurately and it strongly indicate a primordial spectrum that is nearly scale-invariant, just as the inflationary scenario predicts.However, WMAP observations were not sensitive enough to test the non-Gaussianity o f the primordial spectrum and trans-Planckian corrections to the scale-invariant spectrum. It is expected that the sensitivity of the future CMB experiments, like PLANCK, can provide with the form of the corrections to the scale-invariant and stringent constraint on non-Gaussianity of the primordial perturbation spectrum. I am interested in both building and testing new theoretical extensions to standard models. My proposed research strategy is two pronged: development of new theoretical solutions to pro blems of cosmology and to use cosmic microwave background (CMB) as a tool to probe new physics near the scale of inflation.Over the last couple of years, I have been involved in obtaining the power-spectrum, for trans-Planckian inflation, models from the gauge-invariant perturbation theory. I intend to investigate further on the trans-Planckian models to exactly quantify the power spectra and to compare it with the current CMB data. I also plan to investigate non-Gaussianity, along the line of Maldecana (2003), in the trans-Planckian inflationary model and to look for the generic features, which can be tested in the future experiments like PLANCK.