"Supermassive binary black holes: current observations and future prospects"

Lying at the intersection of physics and astronomy, black holes provide a laboratory to study some of the most fundamental questions regarding the physical laws of the universe and the origins of the structures that we live in today. In particular, the study of supermassive binary black holes (SBBHs) is of interest for multiple topics in astrophysics, ranging from the detection of low-frequency gravitational waves to the cosmic evolution of galaxies and galactic nuclei. While the formation of SBBHs from hierarchical galaxy mergers is almost inevitable, direct evidence remains uncertain. Over the past few years, systematic searches using large surveys, combined with multi-wavelength follow-ups, have started to enable investigation of the frequency and demographics of SBBHs down to the gravitational wave regime in the low-redshift universe. I will review the results from these searches and discuss future prospects to observe SBBHs at uncharted merger stages across cosmic time.