A method of fabricating a metamaterial is provided, comprising providing a sample of engineered microstructured material that is transparent to electromagnetic radiation and comprises one or more voids, passing through the voids a high pressure fluid comprising a functional material carried in a carrier fluid, and causing the functional material to deposit or otherwise integrate into the engineered microstructured material to form the metamaterial. Many microstructured materials and functional materials can be used, together with various techniques for controlling the location of the integration of the functional material within the microstructured material, so that a wide range of different metamaterials can be produced.