The Light-Emitting Swallowtail
Though tiny, the scales of the swallowtail butterfly's wing are similar in design to light-emitting diodes. We say similar because the design is closer to a specialized light-emitting diode that puts out six times as much light as a standard LED.
The blue-green wing of the swallowtail is covered with millions of tiny scales. Each microscopic scale has three layers. The top layer is made up of thousands of hollow cylinders shaped in a honeycomb pattern. There is fluorescent pigment within the sides of those cells. The second layer adds the blue-green color to entering light, and the bottom layer reflects it back out. As the light enters, the top layer focuses and reflects all the blue-green light that enters it. The second layer turns any other color entering light – including ultraviolet light – blue-green, and the bottom layer reflects it back out.
The efficiency of the delicate structure has been compared to LEDs that have two-dimensional photonic crystals that put out six times as much light as a regular LED. As one scientist put it, they had no idea that the design would be so "precise" and "refined."
Of course it's precise and refined, showing an understanding of light! It was designed by the same Creator Who created light in the first place.