Habitats from cryo-environments —such as the Arctic, Antarctic, and high-altitude regions—are some of the most fragile, understudied, and climate-sensitive ecosystems on Earth, making them highly vulnerable to climate change. Despite their apparent dormancy, they harbour specialized microbial and viral communities along with unique biogeochemical processes, now increasingly revealed through advances in metagenomics, transcriptomics, and other molecular techniques. This session invites experts in microbiology and biogeochemistry who, drawing on their knowledge of cryo-environments and their complex dynamics, investigate microbial and viral diversity — including microorganisms with unique biotechnological potential—, carbon storage, and nutrient cycling. Their unique and interdisciplinary research aims to understand these ecosystems thoroughly, helping to anticipate their future responses to a warming world.