Two galaxy clusters collided to create the “Bullet Cluster,” shown here. Normal matter is shown in pink and the rest of the matter is illustrated in blue, revealing that dark matter dominates this enormous cluster.

X-ray: NASA/CXC/CfA/M.Markevitch et al.; Optical: NASA/STScI; Magellan/U.Arizona/D.Clowe et al.; Lensing Map: NASA/STScI; ESO WFI; Magellan/U.Arizona/D.Clowe et al.