Visual comparison of a small region in the simulations (left: standard model of cosmology; right: dynamical dark energy model). The differences are subtle but still clearly visible at the substructure level. Visual comparison of a small region in the simulations (left: standard model of cosmology; right: dynamical dark energy model). The differences are subtle but still clearly visible at the substructure level. (Image: ALCF Visualization and Data Analytics Team and the HACC Collaboration)