Active Galactic Nuclei (AGN), powered by supermassive black holes, are among the brightest X-ray sources, with some quasars emitting X-rays 10 billion times the power of the Sun. The most distant black hole detected in X-rays, UHZ1, was found just 470 million years after the Big Bang, with a mass between 10 and 100 million Suns. Another rapidly feeding black hole, LID-568, was discovered 1.5 billion years after the Big Bang, accreting matter over 40 times its theoretical limit.