This interdisciplinary proposal has the objective to greatly enhance our understanding of fundamental biomineralization processes involved in the formation of calcium carbonates by marine organisms, such as corals, foraminifera and bivalves, in order to better understand vital effects. This is essential to the application of these carbonates as proxies for global (paleo-) environmental change. The core of the proposal is an experimental capability that I have pioneered during 2008: Dynamic stable isotopic labeling during formation of carbonate skeletons, tests, and shells, combined with NanoSIMS imaging. The NanoSIMS ion microprobe is a state-of-the-art analytical technology that allows precise elemental and isotopic imaging with a spatial resolution of ~100 nanometers. NanoSIMS imaging of the isotopic label(s) in the resulting biocarbonates and in associated cell-structures will be used to uncover cellular-level transport processes, timescales of formation of different biocarbonate components, as well as trace-elemental and isotopic fractionations. This will uncover the origin of vital effects. With this proposal, I establish a new scientific frontier and guarantee European leadership. The technical and scientific developments resulting from this work are broadly applicable and will radically change scientific ideas about marine carbonate biomineralization and compositional vital effects.