The session will review the current state of knowledge on mercury research in the Southern Hemisphere and tropical regions, encompassing four compartments: (1) Historical emissions and trade; (2) Atmosphere; (3) Land and water; (4) Biota. Our aim is to unveil the uniqueness of the mercury biogeochemical cycle and historical emissions and use in the Southern Hemisphere and highlight key knowledge gaps, enabling new insights into the hemispheric and global cycling of mercury.