Illustration showing the competing effects of dark matter (23% of the universe) and dark energy (73% of the universe) over the lifetime of the universe. Dark energy began to assume prominence about 5 billion years ago. - http://astronomy2009.nasa.gov/topics_oct.htm
Dark matter is an invisible material that emits or absorbs no light but betrays its presence by interacting gravitationally with visible matter. This image from Dark Universe shows the distribution of dark matter in the universe, as simulated with a novel, high-resolution algorithm at the Kavli Institute of Particle Astrophysics & Cosmology at Stanford University and SLAC National Accelerator Laboratory.