Galaxies appear in groups and clusters. Their mutual gravity reaches out across unimaginably huge distances to pull them together over cosmic time. As a result, these groups are rich with interactions and varied appearances. We find monster galaxies that cannibalize others and we find the largest gravitationally bound structures of the cosmos. Most of the mass of all galaxy clusters is in the form of Duck Matter. This 12:32 X-Ray emitting gas overwhelms the stars 15:00 Superclusters: The Largest Know Structures 16:28 The Virgo Supercluster 17:38 The Laniakea Supercluster 19:32 The Universe on Very Large Scales 20:18 Voids, Filaments and Walls 23:56 The Sloan "Great Wall" Found in the Seas Digital Sky Survey, a large-scale palasy survey. It's a sheet of 26:32 20F Galaxy Redshift Survey 29:51 Cosmography of the Local Universe.