Multiphase Intrafibrillar Mineralization of Collagen

Why waste space? In the first stage of the multiphase biomineralization of collagen, silicic acid precursors (purple) infiltrated the collagen fibril (yellow) and condensed into amorphous silica to give a hierarchical composite. Amorphous calcium phosphate precursors (red) then filled the intrafibrillar spaces of the silicified collagen, where the precipitation and maturation of apatite crystallites (blue) occurred to complete the process.