"It's the gravity that shapes the large scale structure of the universe, even though it is the weakest of four categories of forces." -Stephen Hawking
Galaxies don’t just exist in isolation in our Universe, but are often found bound together as a part of even grander structures. Our own Milky Way is bound in a galactic group (our local group), nearby are larger groups and galaxy clusters, and on still larger scales, cosmic superclusters appear to encompass as many as 100,000 individual galaxies.