The thirteen billion year history of the most massive black holes in the universe

Super-massive black holes that are found in the centers of most galaxies started their growth whenthe universe was about 300 million years old. Some of these early "seed black holes" were probablythe remnants of the earliest stars. The most massive black holes, that are some10^10 times more massive than the sun, accumulated most of their massduring the first 3 billion years after the big bang. The less massive ones are still growing today. I will describe a large project to follow black hole evolution with several ground-based and space telescopes.The observations allow us to probe the nature of the most energetic growth episodes and related them to very fast star formation in merging galaxies.We also find additional clues for a parallel evolution of giant black holes and the galaxies that we observe today.