  Wide field imaging is key to understanding the build-up of distant clusters
and their galaxy population. By focusing on the so far unexplored outskirts of
clusters, where infalling galaxies first hit the cluster potential and the hot
intracluster medium, we can help separate cosmological field galaxy evolution
from that driven by environment. I present a selection of recent advancements
in this area, with particular emphasis on Hubble Space Telescope wide field
imaging, for its superior capability to deliver galaxy morphologies and precise
shear maps of distant clusters.
