Studies show that massive galaxies host massive black holes at their centers, and the mass of these "monster" black holes is related to the velocity of stars around the galaxy. Studies of two galaxies, NGC 3842 and NGC 4889, revealed they contain two of the most supermassive black holes known, with masses of around 9.7 billion and 9.8-27 billion solar masses respectively. Future research promises to provide better data on the growth of massive black holes in the universe through improved instrumentation.