In this study, we propose and demonstrate a novel methodology to fabricate nanomaterials with predictable morphologies and physical/chemical properties. This new fabrication methodology typically comprise the following steps: (i) precursors with specific morphology are coated with mesoporous silica; (ii) the precursors are converted into the target products chemically through the channels of mesoporous silica; (iii) the silica coating shells are removed by NaOH solution or other solutions, leading to the final product. The morphology of the final product is insensitive to external experimental conditions, and only determined by the morphology of the precursors. As a test vehicle, uniform Bi0.96Eu0.04PO4 nanospheres with high light emission efficiency have been successfully fabricated by using Bi0.96Eu0.04 nanospheres as the precursors. This novel fabrication methodology can also be extended to design and fabricate nanomaterials with controlled morphology in other material systems.