One of the most abundant minerals in nature and consequently one of the most intensively examined precipitation system is calcium carbonate, CaCO3. CaCO3 polymorph aragonite is the major mineral component in corals. Due to the considerable susceptibility of corals on temperature changes, the global warming is one of the greatest threats for corals and coral reefs existence. In addition the increased atmospheric CO2 reacts with sea water and causes its acidification, which may influence the CaCO3 precipitation in calcifying organisms such as corals. An accurate evaluation of global warming effects on corals requires the knowledge of coral mineralization processes that is still poorly understood The objective of the proposed visit is to study the influence of natural acidic macromolecules, extracted from the skeleton of sea corals, on precipitation of CaCO3 polymorphs, calcite and aragonite. For this purpose spontaneous precipitation of CaCO3 will be investigated in different model systems. The variety of chemical-physical and biological techniques that will be used during the visit will give the main applicant excellent training in a multi-disciplinary research of biomineralization. The main applicant will transfer the gained knowledge to the Ruđer Bošković Institute.