  The structure of the universe is believed to have formed by clustering
hierarchically from small to large scales. Much of this evolution occurs very
slowly but at a few special times more, rapid, violent activity may occur as
major subunits collide at high velocities. The Abell 2125 complex (z=0.247)
appears to be undergoing such an event as shown by modeling of the optical
velocity field and by the detection with the VLA of an unusually large number
of associated radio active galaxies. We present an 80 ksec Chandra imaging of
Abell 2125, together with extensive complementary multi-wavelength data. We
show direct evidence for galaxy transformation and destruction during the
cluster formation. The Chandra data unambiguously separate the X-ray
contributions from discrete sources and large-scale diffuse gas in the Abell
2125 complex, which consists of various merging clusters/groups of galaxies and
low-surface brightness emission. This enables us to study processes affecting
galaxy evolution during this special time from scales of Mpc down to a few kpc.
The overall level of activity plus the special time for the cluster-cluster
merger suggests that an important phase of galaxy evolution can take place
during such events.
