Superclusters of galaxies are the largest collections of massive structures. They occur at the nodes of large numbers of matter filaments in the cosmic web, and are up to a hundred million or more light-years across. There are usually many clusters of galaxies in a supercluster, or a single very large cluster at its center, along with many other groups and collections of galaxies that are collected in the supercluster’s central gravitational field. Superclusters contain many thousands—and sometimes millions—of galaxies. The Milky Way galaxy is located on the outskirts of the Virgo supercluster.