Well-separated and parallel aligned fibers of various polymers have been prepared by a simple but effective melt-drawing procedure, and their structural features have been studied with field-emission scanning electron microscopy. The results show that the resulting polymer fibers, with diameters ranging from tens of nanometers to hundreds of nanometers, consist of highly oriented lamellar or fibrillar crystals with the molecular chains aligned in the drawing direction. Scanning electron microscopy images of the drawing process indicate that drawing a thin polymer molten layer at temperature far above its melting point leads to the formation of elongated microcracks. The microcracks embedded in the polymer thin film propagate along the drawing direction and result in the formation of polymer microfibers, which split continuously under high instantaneous stresses and produce well-separated polymer fibers with diameters on the nanometer scale. (C) 2004 Wiley Periodicals, Inc.