Understanding the formation and evolution of the first supermassive black holes remains one of the most intriguing challenges in modern astrophysics. This talk will focus on three key aspects of early universe AGN studies: radio properties of high-redshift blazars and radio-quiet quasars, examining their jet activity and feedback processes; super-Eddington accretion phenomena observed in both early universe and local AGN populations; and studies of dwarf galaxies as local laboratories for understanding first-generation galaxies. Recent multi-wavelength observations and their implications for black hole growth and cosmic evolution will be discussed, highlighting how these complementary approaches help unveil the nature of the earliest active galaxies.
