Thumbnail Image From YouTube:

This visualization was rendered from the "RarePeak" region in the Renaissance Simulations that follows the formation of 800 galaxies in an over-dense region of the universe when it was only 270 million years old. The blue and red indicates neutral (cold) and ionized (hot) gas.  The white shows where the galaxies are creating ultraviolet light, heating the surrounding intergalactic gas.  This simulation was run on the Blue Waters supercomputer at the National Center for Supercomputing Applications (NCSA).