Nature knows several ways how to capture carbon dioxide (CO2). The most prominent one is photosynthesis, where sun light is used to fix CO2 into biomass. Nowadays, research groups around the world try hard to mimic this process and to realize artificial photosynthesis. The ultimate goal is to efficiently photo-transform CO2 into synthetic fuels. However, nature knows also other strategies for capturing carbon dioxide, such as dissolving CO2 as carbonate (CO32-) in the oceans. Shellfish then make use of the dissolved carbonate and build CaCO3-based solid structures for shelter, which finally end up safely in rocks around the globe.