Part of Hall of the Universe.

Galaxies_HERO AMNH/D. Finnin

Galaxies are the basic building blocks of the universe. Even in a tiny patch of sky, many hundreds can be seen. By surveying such regions, astronomers estimate that there may be 100 billion galaxies in the observable universe. These galaxies are not uniformly spread through space — they commonly occur in pairs, groups, clusters, and superclusters.