All the studies on the deposition of aragonite in scleractinian coral skeletons converge on the concept that it is a biological controlled process, although this process can influenced by environmental parameters. This even if coral skeleton does not show an apparent elegant and accurate architectural assembly of the aragonitic building units as it is in echinoderm and mollusk skeletons. Nevertheless, the OM controls synthesis and microarchitectural organization of aragonitic fibers and the EMCs, producing skeletons having a final morphology which is species specific. This, despite the fact that scleractinian corals have a simple biological structure, when compared with echinoderm and mollusk. Thus, scleractinian corals represent almost an ideal gym for the study of the biomineralization processes. Moreover, there are many clues that multidisciplinary approaches, exploitation of several new experimental techniques and the actual growing interest of the response of coral calcification to OA, will increase even more the interest of all the biomineralization community on these organisms