Schematic illustration of how the galaxy cluster structure scaling depends on the formation epoch of the cluster and on the critical density of the universe in an Einstein-de Sitter (densities are blue) and in a concordance cosmological model (green). The left panel provides a sketch of cluster collapse for a cluster with a formation redshift of z = 0, and the right panel shows a cluster forming at z = 0.5. For further explanations see the text.