Galaxy clusters, which originate from the highest density peaks in the primordial Universe, contain valuable information on cosmology. They are fascinating objects in their own right as they involve an interplay of the physics of dark matter, gas and galaxies. Their complex formation history also leaves observational imprints. We study the shape and the boundary of galaxy clusters and their implications for astrophysics and cosmology. The evolution and dynamics of galaxies in cluster environments are two of the main applications studied in this thesis.