It is currently understood that all large galaxies host supermassive black holes at their centers. Some dwarf galaxies may not contain black holes, but these are not considered "common" galaxies. The presence of the supermassive black hole in the center of galaxies plays a significant role in the formation and evolution of the galaxy; its gravitational effects on stars and gas shape the structures we observe, and galaxies without central black holes would likely evolve completely differently than those we usually observe.