Magnetic granular solids consist of ultrafine metal granules of nanometer sizes embedded in an insulating medium. The magnetic properties are dictated by the nanostructure, which is process controlled. We report on results for granular Fe - SiO2 films where the metal volume fraction and particle size have been systematically varied. Magnetic coercivities as high as 2 500 Oe at low temperatures and 1 100 Oe at room temperature have been achieved.