As for all the biologically-controlled mineralizations, the mineral is precipitated within an organic matrix network responsible for the initiation of this precipitation, the growth and the morphology of the calcification. The organic components are also thought to be involved in the choice of the calcium carbonate polymorph and finally in the stabilization over the time of the amorphous CaCO3 state (biogenic ACC), its purely mineral counterpart being the most unstable polymorph [11,12].