Invoking equations governing the gravitational interaction and the expansion of the universe, cosmologists use supercomputers to simulate the evolution of the universe from a nearly uniform initial state, consistent with microwave observations, to the clumpy arrangement of galaxies observed today. These simulations reveal that the observable pattern of galaxies is anchored by a massive underlying network of dark matter filaments (shown here predominantly in red, yellow, and green) shaped over cosmic time, in part, by the reverse-gravity influence of dark energy. Improved cosmological simulations at los Alamos will help researchers constrain what these dark components of the universe can be. 16 1663 los alamos science and technology magazine october 2012