Abstract: Supermassive black holes power disks, coronae, jets and winds, and a significant fraction of energy released by the black holes may be carried by cosmic rays and associated high-energy non-thermal radiation. Recently, the IceCube Collaboration reported associations of high-energy neutrinos with active galactic nuclei, including a nearby Seyfert galaxy, NGC 1068. We review the implications of the multimessenger data for theoretical models and discuss their challenges.