Active galactic nuclei (AGN) are extremely luminous sources of radiation at the centers of galaxies, powered by the accretion of mass onto a supermassive black hole. AGN are among the most energetic sources in the universe, emitting radiation across the entire electromagnetic spectrum, from radio waves to gamma rays. Research on AGN seeks to understand the physical processes that drive their extreme luminosity, the interactions between the central supermassive black hole and its surrounding environment, and the effects of AGN activity on the evolution of galaxies. Scientists study AGN using a variety of observational techniques, including radio, infrared, optical, and X-ray astronomy, as well as theoretical models and simulations. Overall, research on AGN plays a crucial role in our understanding of galaxy evolution, black hole physics, and the broader implications of supermassive black holes in shaping the universe as we know it.