Astronomers have been able to peer back to the young Universe to determine how quasars — powered by supermassive black holes with the mass of a billion suns — form and shape the evolution of galaxies. Two teams of astronomers have looked back nearly 13 billion years, when the Universe was less than 10 percent its present age, to determine how quasars — extremely luminous objects powered by supermassive black holes with the mass of a billion suns — regulate the formation of stars and the build-up of the most massive galaxies.