Scientists in Switzerland think they have discovered how chameleons change colour, and it's all down to crystals.
Chameleons are famous for being able to change colour to blend into their surroundings.
A team from the University of Geneva have studied how they do it, and found that special crystals in their skin are responsible.
The crystals act as a type of mirror to reflect the colours around the chameleon.
These crystals are found in special skin cells chameleons have.
And these cells don't just help them change colour, they could also help keep them cool by reflecting light.
The study looked into panther chameleons.
It was thought that the colour change happened when the reptiles moved special colour pigment around their skin.
But this latest research thinks that isn't the case, and it's actually down to the special crystals.