My main area of research is the multi-wavelength observations and interpretation of the processes going on around supermassive black holes (BH): the nature of the power source in active galactic nuclei (AGNs); the cosmological evolution of supermassive BH and their host galaxies, and relationships with environment in small and large scales. One of my long-term interests has been the variability of the radiation from AGNs to probe what is going on around the supermassive BH and power generation.