The process of biomineralization has profound impacts on the geology of our planet and is an integral part of the global carbon cycle by generating large amounts of CaCO3 bound in coral reefs, chalk mountains and deep sea sediments. Mounting evidence demonstrate that many marine calcifiers generate biominerals by the intracellular formation of CaCO3 from seawater Ca2+ and metabolic CO2. To date, the underlying mechanisms that control the carbonate chemistry in calcifying vesicles are unknown which however will provide ground-breaking insights into a biological process that is capable of transforming a metabolic waste product - CO2 - into a versatile construction material. In the past 5 years my group has developed a unique methodological expertise to study the cellular physiology of calcifying systems. Building on this expertise CarboCell will tackle the important but challenging task to identify and understand the mechanisms of vesicular calcification. The sea urchin larva will serve as a powerful model organism, that represents a prime example for the intracellular formation of CaCO3 and which allows us to employ specifically targeted molecular perturbations in combination with sub-cellular ion and pH recordings. CarboCell will take a stepwise strategy to systematically examine the mechanisms of vesicular calcification on the three main core subjects- carbonate chemistry (WP1), ion/CO2 transport mechanisms (WP2) and vesicular volume regulation and trafficking (WP3). CarboCell will provide a deep mechanistic understanding of the calcification process with strong implications for explaining and predicting responses of marine calcifiers to the global phenomenon of ocean acidification. More importantly, knowledge about the mechanisms that allow organisms to transform CO2 into a construction material will pave the ground for novel, biology-inspired solutions of CO2 capture and utilization – a basic science approach at the core of twenty-first century concerns.