Low density gas is blue and transparent and high density gas is red and opaque in the display. The highest density "knots" occur at the intersection of filaments and correspond to clusters of galaxies in the simulation.
This simulation uses a mixture of hot and cold dark matter. Here are further details of the calculation.
Usage: Click "Play" to begin. Click "Stop" to pause. "Step" moves forward one frame, and "Back" moves backwards one frame. "Home" returns to the beginning.