My work is focused on Active Galactic Nuclei, i.e. active SuperMassive Black Holes. I am particularly interested in understanding how do they accrete and interact with the surrounding matter. I am currently studying the highest redshift quasars known, to understand how the most massive black holes in the early Universe could form in their (very) short life-time. A large part of my work is devoted to blazars. Thanks to their peculiar orientation, they are the perfect tools to study the role of jets in the physics of Active Galactic Nuclei.