This image is a snapshot of a cosmological simulation zoomed on a single galaxy and its environment when the universe was only one billion years old (today the age of the Universe is approximately 13.8 billion years). Clumps in the map represent the central galaxy and their satellites, while filaments are primordial gas inflowing on the compact objects. This temperature map shows, in blue, the cold gas in the center of the galaxy, her satellites, and filaments of primordial gas inflowing gravitationally on the compact objects. Surrounding the galaxies, depicted in the warm colours tending to yellow, is the hot gas heated via supernovae explosions. This numerical simulation is produced by the Cosmology group of the Scuola Normale Superiore.