How do chameleons change color? Photonic crystals, duh.

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Bit of an old paper (2015) but a good one! Thought it was a cool topic so thought I’d share.

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The Problem

Many animals can change color for camouflage or mating displays, and most do this through grouping organelles in their skin. When grouped, these small sub-cellular features change the actual pigments of the skin.

However, chameleons are a bit different. This week’s paper takes a look at how.

The Solution

There are several ways to get color. The way we’re most familiar with involves the pigment of the object, like our skin, that controls the actual absorption of light.

Another way is through something called structural color. Structural color involves many small-scale (often nano) features on a surface that interfere with light waves and cause us to see different colors.

The size, spacing, and pattern of the nano features all dictate which wavelengths of light get interfered with (i.e. the color). By changing the arrangement, you change the resulting color without ever involving a pigment.

This week’s paper shows that this is what chameleons do.

Instead of relying on pigment changes, they rapidly change their color by reorganizing tiny structures on their skin. As the nano-crystals reorganize, the color of the light reflected from the chameleon’s skin changes (see C above).

And there you have it! Chameleons don’t rely on skin pigmentation for their changing color, but on an actual structural feature of their skin.

See you next week for more science,

Neil