This study demonstrates a simple and highly reproducible method for fabricating well-defined nanostructured polymeric surfaces with aligned nanoembosses or nanofibers of controllable aspect ratios, showing remarkable structural similarity with interesting natural biostructures such as the wing surface of Cicada orni and the leaf surface of Lotus. Our studies on the present biomimetic surfaces revealed that the wetting property of the nanostructured surface of a given chemical composition could be systematically controlled by rendering nanometer-scale roughness. The nanofabricating method we developed can be readily extended to other thermoplastic polymeric materials (e.g., light-emitting polymers, conducting polymers, block copolymers, liquid crystalline polymers), and it could be applied to developing a new generation of optical and electronic devices.