Calcium carbonates make up some of the most abundant minerals in the world. They are of great importance in geology and in the field of biomaterials as well as having several industrial applications. Despite the high interest, detailed structural information on several calcium carbonates still does not exist. This is especially true for amorphous calcium carbonate, a kinetically stabilized intermediate, also in biological mineralization. Therefore, solving the structure of ACC would increase our understanding of the formation of complex hierarchical biomaterials. Traditionally this has been attempted with MAS-NMR, EXAFS, RAMAN and many other techniques. However, this only gives information on the closest coordination sphere. By performing Neutron PDF on standardized ACC we intent to characterize the structure of ACC with emphasis on the structure of water inside the ACC.