Imagine a bill covered with microscopic holes that make it glow slightly in the light. It's tech borrowed from a butterfly, and it may soon be foiling counterfeiters around the world.

If all goes as planned, the world's supply of cash will soon be secured with a nano-scale optical defense that is as secure as it is visually impressive. Using arrays of holes no bigger than a virus, scientists at Toronto-based Nanotech Security have created an atoms-thick display that can be read by humans or machines and that shines with the brightness of a typical LED despite using nothing but reflected light.

The technology was inspired by the Blue Morpho butterfly, whose brilliant blue coloration comes not from pigment but the way that tiny holes in its scales reflect light. But the tech, called Nano-Optic Technology for Enhanced Security (NOtES), is different from the Morpho butterfly's wings, and pretty much all other bio-inspired reflective optical technologies, in that it is both extraordinarily thin and functions even in dim light.