Calcite Crystal Growth by a Solid‐State Transformation of Stabilized Amorphous Calcium Carbonate Nanospheres in a Hydrogel

An ugly duckling grows into a swan: Many organisms grow their crystalline mineral phases through the secondary nucleation of nanospheres made of an amorphous precursor phase. Stable amorphous calcium carbonate biominerals were used to induce a similar transformation in vitro. The amorphous nanospheres underwent a solid-phase transformation that resulted in highly ordered calcite crystals composed of aggregated particles (see SEM image).