Butterfly wings that are "identical in design to the LED."

BBC reports:

This slab of hollow air cylinders in the wing scales is essentially mother nature's version of a 2D photonic crystal.

Like its counterpart in a high emission LED, it prevents the fluorescent colour from being trapped inside the structure and from being emitted sideways.

The scales also have a type of mirror underneath them to upwardly reflect all the fluorescent light that gets emitted down towards it. Again, this is very similar to the Bragg reflectors in high emission LEDs.

"Unlike the diodes, the butterfly's system clearly doesn't have semiconductor in it and it doesn't produce its own radiative energy," Dr Vukusic told the BBC News website "That makes it doubly efficient in a way.

"But the way light is extracted from the butterfly's system is more than an analogy - it's all but identical in design to the LED."...

"When you study these things and get a feel for the photonic architecture available, you really start to appreciate the elegance with which nature put some of these things together," he said.

No, I'm not trying to restart the Intelligent Design debate. I just think it's cool.