The large variation in inorganic structures encountered in biological systems, often with exquisite and unique morphologies, has fascinated researchers in all scientific disciplines for a long time. [1] For materials scientists, an understanding of the principles underlying the process of biomineralization holds great promise for the design and synthesis of new inorganic and hybrid structures with yet unrealized properties. The central concept in biomineralization research is that organized biomacromolecules, which contain well-defined arrays of functional groups, control polymorph selection and the oriented nucleation of crystals by lowering the nucleation energy of specific crystal faces. [2] Control over crystal morphology is then exerted by the interaction of biomolecules in solution with specific crystal planes during growth.
Recently, it has become clear that the classical concept, which proposes that a template containing well-defined arrays of functional groups controls the nucleation of the inorganic crystals by geometric and stereochemical matching, needs expanding. [3] Furthermore, a crucial role for amorphous calcium carbonate as a transient intermediate has been proposed. [4] In the last few years it was demonstrated that specific nucleation of calcite can be achieved without an