Absorption line studies through high redshift quasars offer a powerful way to explore the atomic gas distribution in high redshift galaxies and in the intergalactic medium. With large spectroscopic surveys such as SDSS, the statistics of absorbers are currently well known at z > 2. In particular, absorption line studies yield an excellent measure of the column density distribution (i.e. the number of absorbers per comoving volume inintervals of column density). Folded into this distribution, there are information on the size of the absorbers, their number density, and even how gas is distributed spatially in individual systems (e.g. in disks, inflows or outflows). Aiming to disentangle these properties, we started an imaging survey of quasar fields to identify the optical counterparts of the absorbing galaxies. These observations allow us to directly measure the gas distribution in high redshift systems and, for the first time, the luminosity function of HI selected galaxies at z > 2. In addition to these observations, we use high resolution galaxy simulations to quantify what is the contribution of (massive) galaxies to the observed absorption line statistics. In fact, with simulations, we can separate features imprinted by galaxies on the column density distribution from those due to the intergalactic medium. Combined together, images and simulations enable a detailed study of the atomic gas in the high redshift universe.