Gucci pocketbooks, Rolex watches and banknotes. What do they all have in common? They have value and there are a lot of fake ones around. In the US over the past couple of years, there are new banknotes that have things in them to reduce the problems of counterfeiting. Now some scientists at Simon Fraser University in Canada are trying to use nanotechnology to prevent bad guys from counterfeiting money. Their inspiration is the blue morpho butterfly which has a cool iridescent blue color. The color is produced when light reflects off the surface—a surface that has nanoscale features which diffract only a narrow spectrum of light. No color pigment that can be copied but only features that can be fabricated into the banknote. Some day these things to prevent counterfeiters could be used in a lot of different kinds of objects.