The hadal zone encompasses ocean trenches deeper than 6,000 meters. Named after Hades, the Greek god of the underworld, these are the most extreme environments on Earth. The Mariana Trench, the deepest known point at approximately 11,034 meters, is home to xenophyophores — giant single-celled organisms — and snailfish that have adapted to pressures exceeding 1,000 atmospheres. Recent expeditions have even discovered amphipods and bacteria thriving in the deepest reaches, challenging our understanding of life's limits.