A liquid-crystalline (LC) polymer melt coating a glass support shows a remarkable wetting ridge pattern resulting from a "stick-and-break" phenomenon when submerged into water at a velocity of 20 cm/s. A series of parallel, regularly spaced wetting ridges of 0.2 mu m height are formed perpendicular to the advancing direction of the plate at 1 mu m intervals, and the pattern continues over a wide area (1 x 2 cm(3)). The ridges function as a narrow line diffraction grating, similar to a prism that separates white light into the spectrum of colors. This process provides new insight into the controlled nanofabrication of polymers that is low-cost and high-throughput.