Calcium carbonate nanoparticles were generated beneath the Langmuir monolayer of bovine serum albumin (BSA) via templated mineralization. The BSA monolayer and calcium carbonate nanoparticles were characterized based on the measurement of surface pressure-area (pi-A) isotherms and area-time curve, and analyses of transmission electron microscopy (TEM), selected area electron diffraction (SAED), scanning electron microscopy (SEM), and X-ray diffraction (XRD)as well. The interaction mechanisms between BSA and calcium carbonate and the role of amorphous calcium carbonate (abridged as ACC) and lattice match in controlling the morphologies and microstructures of the target Calcium carbonate (CaCO3) crystals were discussed, and a model was suggested to illustrate the formation of CaCO3 crystals in the presence of the BSA monolayer. Results indicated that the calcium carbonate nanoparticles were formed through a multi-step process in the presence of the BSA monolayer. Both the amorphous calcium carbonate and lattice match played important roles in terms of the controlled biomineralization and organic matrix-mediated synthesis of CaCO3 nanoparticles. The transformation of amorphous calcium carbonate phase to calcite crystal phase could provide direct evidences to the multistep crystallization process in biomineralization. And the present approach could be used to guide the synthesis of advanced inorganic nanomaterials via simulated biomineralization under mild conditions. (C) 2008 Elsevier B.V. All rights reserved.