The Critical Zone Network of Networks (CZ-NoN) is a new international project that brings scientists together to study the Critical Zone—the thin layer of Earth where rock, soil, water, air, and life interact to support ecosystems and people. Supported by the U.S. National Science Foundation, CZ-NoN connects existing research sites and monitoring programs around the world to help tackle big environmental challenges that no single site or team can solve alone. The project promotes communication, data sharing, and collaboration through meetings, workshops, webinars, and outreach. It also invites input from researchers worldwide to identify key questions for future study. By encouraging cooperation and building on what already exists, CZ-NoN helps scientists work together to better understand how the Earth’s surface functions and changes.