In his words:

The data showcased here are part of the “Millennium Simulation,” a computer model that employed more than 10 billion particles of matter to trace the evolution of a 2 billion light-year cubic region of the Universe; the largest ever model of its kind at the time (Springel et. al, 2005). Simulations such as these can reveal the physical processes underlying the build-up of real galaxies and black holes.