We have developed a new method with which we can for the first time produce self-aligned cobalt silicide (CoSi2) nanostructures from Co nanoparticles. These nanostructures are formed by reacting Co nanoparticles with Si substrates at 900degreesC. Their dimensions are normally 3 to 10 nm wide and up to a few micrometers long. The orientations of these nanostructures are controlled by the crystalline substrate, as they are orthogonally and hexagonally aligned on Si(100) and Si(111), respectively. Because these self-aligned nanostructures (SAN) are thermally stable up to 1000degreesC in air and chemically inert to prolonged treatment with strong acids, and because their sizes are uniform and much smaller than those made from lithography, they can be ideal materials for making components such as electric contacts, interconnects, and gates for future nanoelectronics.