Galaxy clusters are thought to be the largest gravitationally bound objects in our Universe. EU-funded astrophysicists study the available wealth of observations to confirm theories of their evolution through cosmic time.
As vast as our sprawling galaxy may seem, the Milky Way is but a speck next to galaxy clusters. These collections of hundreds to thousands of galaxies bound together by gravity grow continuously by accreting mass from their surrounding intercluster medium (ICM).
Further details: Galaxies drifting through the cosmic web