Hidden away deep in a Central African forest is something quite special. The Pollia berry's name doesn't quite do it justice, because this thing is shiny. Damn shiny. In fact, it's the shiniest living thing in the world.
These fruits, which look a bit like something you might hang on a Christmas tree, owe the title to their microscopic physical structure. In fact, it might shock you to hear that they contain no blue pigment whatsoever.
The surface of the berries is actually made of four layers of thick-walled cells, each layer itself containing more layers made of cellulose fibres. All those fibres run parallel in their own layer, but the layers are all slightly rotated relative to each other, forming a spiral when you look from the top down.
That means that when light hits the structure, some light is reflected by each layer of fibres in such a way that the light bouncing back is amplified -- a concept known as constructive interference -- to produce remarkably strong colours. The result is very shiny -- shinier than any other living thing on the planet. Just don't bother eating them, because apparently they contain virtually no nutritional content whatsoever. [PNAS via Not Exactly Rocket Science]