Five billion light-years away lies MACS J0717, a system of unprecedented collisions. This image, a composite of x-ray (blue, violet) and optical (cyan, yellow) wavelengths from multiple telescopes, captures the first documented merger involving four galaxy clusters, each of which is a massive gravitationally bound grouping of galaxies. (This labeled version shows the location of the individual clusters and the direction of motion for the speediest among them.) Such mergers are violent events: one of the clusters in MACS J0717 is racing through the system at approximately 3,000 kilometers (2,000 miles) per second. The entire structure is several million light-years across—for comparison, our Milky Way Galaxy is approximately 100,000 light-years in diameter.