Galaxies are thought to form primarily through the merging of smaller galaxies and the accretion of cold gas from the intergalactic medium (IGM). The aim of this project is to directly detect the low mass building blocks of present-day galaxies like the Milky Way and the signatures of gas transport from the IGM into gaseous halos and disks. The collaborating team will make use of spectroscopic observations that can provide higher contrast between faint galaxies and the sky background than broad- or narrow-band imaging, and will take advantage of recent increases in instrumental sensitivity and their access to large telescopes. The team will carry out 4 distinct sub-projects: (1) Spectroscopic searches for Lyman-alpha emission from the IGM and high redshift galaxies. The aim is to reveal the spatial extent, kinematics and energetics of gas in the early stages of galaxy formation. (2) Line-profile analysis of bright Lyman-alpha galaxies. The data will be used to constrain the relative importance of infall and outflow in galaxies. (3) High resolution spectroscopy of MgII absorption systems in the spectra of background quasi-stellar objects (QSOs). These data will be used to understand the origin of cool gas clouds in galaxies without current star formation. (4) A deep, two-dimensional Balmer-alpha search of local galaxies in an effort to detect cool halo clouds condensing from the halo onto the disk. These projects are intended to be available as doctoral dissertation projects for graduate students in the Carnegie Institution's pre-doctoral fellowship program. The Principal Investigator will also participate in supervising undergraduate students from the Claremont Colleges in astronomy research.