  Galaxies in the local universe are most commonly found in groups and are
thought to be "pre-processed" in this environment before being consumed by
clusters. Yet we know very little about the gastrophysics of these systems, how
they evolve and how this environment is connected to the quenching of
star-forming galaxies. In particular, the role of intragroup gas has been
challenging to uncover due to observational constraints and the limitations of
radio telescopes to date. Sensitive, interferometric \HI\ observations of
galaxy groups, combined with multiwavelength tracers of stellar mass, star
formation and shocks, is necessary to examine the physical processes
transforming galaxies from star-forming to quenched. These laboratories may be
key to understanding the dominant mechanisms driving galaxy evolution. MeerKAT
uniquely combines a large field of view, column density sensitivity, and
excellent UV coverage on short baselines ensuring sensitivity to diffuse gas.
This design makes it a compelling instrument for the study of intragroup and
circumgroup gas, quenching in galaxy groups, and for tracing evolutionary
pathways within the group environment.
