Structure in galaxy clusters
  We will discuss here how structures observed in clusters of galaxies can
provide us insight on the formation and evolution of these objects. We will
focus primarily on X-ray observations and results from hydrodynamical $N$-body
simulations. This paper is based on a talk given at the School of Cosmology
Jose Plinio Baptista -- `Cosmological perturbations and Structure Formation' in
Ubu/ES, Brazil.
