  Observations of the Galactic ISM have had tremendous impact on our
understanding of the physics of galactic gas and the processes of galaxy
formation. Similar observations at z>2 reveal the neutral baryonic content of
the universe, trace the evolution of metal enrichment, shed light on process of
nucleosynthesis and dust formation, and yield precise measurements of galactic
velocity fields. Owing to the limitations of UV spectroscopy, however,
researchers are unable to examine galactic gas at 0<z<2, an epoch spanning ~80%
of the current universe. To complement the multitude of ongoing programs to
identify and research z<2 galaxies, a next generation space telescope is
essential to investigate the gas which feeds and records the history of galaxy
formation.
