We've all heard of a mood ring but this is something else!
Something spectacular was unveiled at London Fashion Week and it had nothing to do with clothes.
Lauren Bowker, who describes herself as a 'textile alchemist' has previously made garments that react to feelings and the wearer's environment.
But now she has turned her hand to hair dye and the results are breathtaking...
The dye has been created by a company called The Unseen and comes in multiple colour ranges.
The clip above is called FIRE and reacts to different temperates around the model changing her hair from bright reds to darker tones - so clever!
So how does it work? Here's the science-ey bit...
Above a certain temperature, one of the molecules comprising the carbon bond in the hair dye becomes unstable and therefore its level of light absorption differs creating a different colour.
If you're worried that this crazy dye might harm your hair, Bowker reassures that
"Because of how we've formulated the dye, we're confident there will be no damage to the scalp, and no significant effect on the hair fibres themselves (no more then typical semi permanent dyes that is.)"