Using an integrative -omics approach, the research group of Prof. Steindler provide evidence for sponge‐hosted bacterial methane synthesis occurring in fully oxygenated shallow‐water habitats. They suggest methane generation occurs via at least two independent pathways involving methylamine and methylphosphonate transformations. Given the global distribution of this ancient animal lineage and their remarkable water filtration activity, sponge‐hosted methane cycling may affect methane supersaturation in oxic coastal environments. Depending on the net balance between methane production and consumption, sponges may serve as marine sources or sinks of this potent greenhouse gas.