The development of all-epitaxial metal/semiconductor nanocomposite systems by MBE (molecular beam epitaxy)-growth represents a novel and unique approach to the fabrication of precisely defined nanoscopic architectures that cannot be produced using conventional techniques. Such an approach will open up an entirely new class of materials with enormous implications for electronic devices that have the potential for new and improved performance/properties when compared to previous semiconductor technologies, thus providing materials science challenges well into the next decade.