My research work is focused on unraveling the physical mechanisms responsible for evolution of the Intergalactic Medium (IGM). I am particularly interested in understanding how and when the Reionization of the IGM took place, as well as constraining the information about the sources that drove this last major phase transition that occurred in the Universe. Specifically, I study how the enhanced radiation field in the so-called proximity zones around luminous quasars changes the ionization and thermal state of the surrounding IGM. I approach this complex problem using the combination of hydrodynamical simulations and 1D radiative transfer algorithms, and Ly-alpha tomography.