Semiconductor wire-like microstructures with nanometer-scale dimensions have been grown by a selforganized technique. This fabrication is based on organometallic vapour-phase epitaxy (OMVPE). Gold is a key material for growing such nanometer-cylinders (called whiskers). Artificially controlling the gold deposition and the subsequent self-organized growth process resulted in successful control of diameter, length, and growth position of whiskers. Low-damage quantum-wire structures were fabricated which showed quantum confinement effects for electrons in quasi one-dimensional-structures. As an application of these structures, GaAs whiskers with p-n junctions were grown and used in quantum-wire light emitters.