In this paper, we introduce a technique by which the internal
material properties of an object can be optimised at a microstructural level (5x10-5m) to counteract the forces that are applied to it. These can then be fabricated using the rapid prototyping method of stereolithography. The proposed technique is analogous to principles of mass customization and takes advantage of a flexible module to create complex structures in a manner that is computationally efficient and effective. The process is two-staged, in which a genetic algorithm evolves the topology of the microstructure and a second algorithm incorporating Finite Element Analysis then optimises the geometry. The examples shown are designed specifically for the fabrication technique, but the method and general principles are applicable to structural problems at any scale.