In this activity, learners use UV light to transfer a pattern onto a plastic board. The pattern is transferred by placing a mask (a transparency sheet with the pattern) on a plastic board. The board is coated with a copper film that is covered with a light-reactive polymer (photo-resist). The polymer is exposed to UV light through the mask to make a pattern in the polymer. The metal under the exposed polymer is then chemically etched, leaving only the pattern on the surface of the board as determined by the mask. This top-down approach to nanotechnology is commonly used in manufacturing circuit boards for computers and other electronics.