A method is provided for growing mono-crystalline nanostructures onto a substrate. The method comprises at least the steps of first providing a pattern onto a main surface of the substrate wherein said pattern has openings extending to the surface of the substrate, providing a metal into the openings of the pattern on the exposed main surface, at least partly filling the opening with amorphous material, and then annealing the substrate at temperatures between 300° C. and 1000° C. thereby transforming the amorphous material into a mono-crystalline material by metal mediated crystallization to form the mono-crystalline nanostructure.