Contrary to popular belief, chameleons' amazing colour changing abilities have nothing to do with camouflage. Different species of chameleon have varying degrees of colour-changing ability. Some are able to splash vibrant patterns across their bodies, whilst other are limited to a few specific colours or even just various shades of brown. There are lots of different reason why a chameleon might change colour. For example, if Mr Chameleon is a little chilly, he might turn a deep shade of brown in order to absorb more warmth from the sun. If he gets too hot, he'll make his skin lighter to reflect more of the sun's rays instead. Colour changing is also used as a method of communication, signalling everything from aggression to sexual availability. Female Panther chameleons, for example, will turn their usually light brown skin dark brown with orange stripes when they are pregnant, in order to signal to Mr Chameleon that she's definitely not interested. As well as why chameleons change colour, how they do it is also fascinating. It was thought for a long time that chameleons change colour by dispersing different pigments underneath their skin, but it's actually a little more complicated than that. They actually have layers of nanocrystals under their skin that they can manipulate to reflect different wavelengths of light. By grouping them close together, shorter (i.e. bluer) wavelengths are reflected, space them out and the longer, redder, wavelengths are. If you apply pressure to the skin, it compresses these crystals slightly, leaving a blue spot behind. But please don't go around squishing chameleons, it's a good way to get banned from the zoo.
