Neutral gas in galaxies makes up only a tiny fraction of the total cosmic
baryon content. However, studying this gas is important for many reasons:
it is the fuel for star formation, a good tracer of galaxy dynamics, an excellent
search tool for missing satellites, an indicator of galaxy interactions, etc. 
In this talk I will review what we have learned from undertaking large scale
surveys for neutral gas, and in particular compare our studies at z=0 what
results from quasar absorption lines at higher redshifts. What does such a 
comparison tell us about the cosmic star formation history and the evolution 
of the cosmic gas content. How does it help us to plan future surveys with 
telescopes such as the SKA and ALMA?