Fig. (2) Timeline of molecular and cellular B-G reactions (modified after reference [4]). The process starts with five inorganic stages that occur very rapidly on the surface of B-G particles and lead to formation of polycrystalline HCA. The latter fastens down rapidly with the surrounding tissue from step 6 and acts as framework for the ingrowth of new bone. 3D architecture of mineralized bone is created by mesenchymal stem cells in response to critical concentrations of the soluble ionic constituents released from B-G. Mineralization of the matrix follows thereafter and mature osteocytes, encased in a collagen-HCA matrix, are the final product by 6-8 days in vitro and in vivo.