Supermassive black holes or SMBHs were some of the largest black holes in the universe. Supermassive black holes were defined as having a mass greater than a million yellow stars put together. They were so powerful that they could hold together an entire galaxy and bend the light of its stars. Almost all galaxies had supermassive black hole at their cores. For centuries, SMBH's were believed to be the most massive single objects in the universe. However, some black holes outside the Galaxy were reported to be even larger (see Hypermassive black hole)