The deep ocean covers more than 65% of the Planet’s surface and hosts Earth’s largest reservoir of microbial biodiversity. Yet, a fundamental part of this system remains largely unknown. In recent years, increasingly sophisticated technologies and cutting-edge research infrastructures have allowed us to observe and study the unexplored: a journey through oceanographic vessels, underwater robots, deep-sea cameras, deep-core sampling, and innovative analytical techniques that are helping us unravel the mysteries of life in the marine abyss.