Novel potentials of calcium silicate ceramics for environment-friendly material applications are briefly described based on experimental and computational simulation methods. Calcium phosphate clusters were successfully incorporated into the structure of tobermorite under hydrothermal reaction conditions. The incorporation of the cluster resulted in changes in the crystal structure and density of states of tobermorite, thereby improving the biocompatibility of the resulting material. The chemical composition of the hydrogarnet could be controlled using a potassium solution during hydrothermal reaction in a CaOSiO 2 Al 2 O 3 H 2 O system. This afforded tailoring of the content of the surface hydroxyl groups. Consequently, this led to enhanced adsorption abilities towards organic compounds in solution.