  Galaxy groups and low-mass clusters provide important laboratories in which
to study X-ray gas physics and the interplay between galaxy evolution and
environmental effects. The X-ray Multi-Mirror (XMM) Large Scale Structure (LSS)
survey has currently imaged 5 deg2 to a nominal extended source flux limit of
order 10e-14 ergs/s/cm2 and is dominated numerically by low-mass groups and
clusters at redshifts 0.2 < z < 0.6. We discuss the generation of the XMM-LSS
cluster sample, initial results on the physics of groups and low-mass clusters
and the prospects for detailed follow-up studies of these systems.
