Our understanding of orgin of the universe is mainly in frame work of Big-Bang models. Stringent constraints on these models come from light element abundances and thermal evolution of cosmic microwave background. Development of structures in the Universe very much depends on the mass density of different components and their redshift evolution.Development of fundamental physics relies on the constancy of various fundamental quantities such as the fine structure constant. Detecting or constraining the possible time variations of these fundamental physical quantities is an important step toward a complete understanding of basic physics.High quality absorption lines seen in the spectra of distant QSOs allow one to address all the above listed issues. In this talkwe will present the overview of the approach and highlightsome very recent results based on observations taken with VeryLarge Telescope (VLT) in Chile and Giant meterwave radio telescopenear Pune.
