The search for and characterization of dual and binary supermassive black holes (SMBHs) play a crucial role in understanding the co-evolution of galaxies and SMBHs, as well as the mechanisms driving SMBH formation and growth. I will briefly review recent findings in the field, focusing on dual and binary Active Galactic Nuclei (AGN). Current studies cover both low and high redshifts. They include statistical analyses of known AGN pairs with separations up to 100 kpc, the identification of new dual AGN samples with sub-kpc to kpc-scale separations, and the exploration of binary AGN candidates with sub-pc separations.These efforts are particularly significant  for gravitational wave experiments, as binary SMBHs are powerful gravitational wave emitters within frequency ranges where PTA and LISA are most sensitive.

Brief CV of Dr. Paola Severgnini:

Research staff at the INAF-OABrera since 2005.
Paola Severgnini research focuses on Active Galactic Nuclei (AGN), particularly obscured AGN, and more recently, on dual and binary AGN pairs approaching coalescence, critical for understanding galaxy and supermassive black hole evolution and multi-messenger astronomy. 
PS has led several observational projects funded by ASI and she is currently one of the national coordinators of a scientific project on dual and binary AGN, funded by INAF (“Dual and binary supermassive black holes in the multi-messenger era: from galaxy mergers to gravitational waves"). She is also collaborating with national/international working groups on the scientific exploitation of new ground-based EM instruments and future GW missions (LGWA, and LISA).