These reptiles use colour changes to camouflage and to communicate. Swiss researchers discovered that the colour change is not only accomplished with pigments – as has been believed up until then – but also with nanocrystals.
Swiss researchers have discovered how chameleons accomplish their vivid colour changes: they rearrange the crystals inside specialised skin cells.
It was previously suggested that the reptiles’ famous ability came from gathering or dispersing coloured pigments inside different cells.
But the new results put it down to a “selective mirror” made of crystals. 
And – if you are into biomimicry you might have noticed that, too – there is more than one function accomplished by that:
They also reveal a second layer of the cells that reflect near-infrared light and might help the animals keep cool. 
Principle 32 often leaves people a little bit stunned – how might a change in colour solve a technical problem?
However, there are surprisingly many technical parameter pairs where this principle is suggested first to solve contradictions without trade-offs – for example, if you want to enhance Measurement Precision (technical parameter 29) without aggravating Loss of Time (technical parameter 25).
- The usage of coloured liquids helps to detect leakage.
- Fumes are used in wind channels to make turbulences visible.
Sometimes the absence of colour is the key. For instance, if you want to improve the Ease of Operation (technical parameter 33) without compromising the Stability of the Object (technical parameter 13), there are two examples for using transparency.
- Transparent bandages allow for an easy wound check without removing the bandage.
- Transparent tanks allow for an easy fluid level check without opening.
And there are many other examples in our everyday life – just like biological systems we use colour (change) to camouflage, to make aware or to alert.
- In medicine, fluorescence is used as a marker.
- Colour coded labels indicate product sterility or an efficient cold chain. 
With nanocrystals … who knows, maybe the invisible car of James Bond  is not too far away 😉
- Photonic crystals cause active colour change in chameleons » nature.com
- Chameleon colours ‘switched by crystals’ » bbc.com
- Picture of chameleon by courtesy of » Margit Völtz, pixelio.de
- TRIZniks is a fond expression for people who are into the “Theory of Inventive Problems Solving”.
- I use the expression “evo-innovation” for successful inventions by nature, evolutionary proved.
- More examples are to be found here » triz40.com
- Aston Martin V12 Vanquish » jamesbond.wikia.com