Chameleons have long been admired for their color-changing camouflage abilities, but it was a mystery — until earlier this year — how those abilities worked. Researchers at the University of Geneva in Switzerland reported in March that panther chameleons have two layers of epidermal cells dotted with tiny crystals. The tautness of the animal’s skin brings the crystals closer together or further apart, altering the color of light reflected.

When the panther chameleon is relaxed, the crystals are nearer together, according to Nadia Drake of National Geographic. This closeness results in the reflection of blue light.

Crystal-studded cells are not a new discovery in the animal kingdom; butterfly wings, bird feathers, fish scales and beetle carapaces owe their sheen to similar photonic crystals. These make for structural color—a quality that can last much longer than color achieved by the pigments of other animal species.

But the panther chameleon does not use photonic crystals exclusively. Chameleon skin also has pigments. A combination of yellow pigments and loose, relaxed skin makes for a green coloration, for example. As the crystals move further apart, as in a display to attract a mate, the color shifts from green to yellow or red, according to Drake. The full transition from placid green to excited red can take a panther chameleon one to two minutes, according to the University of Geneva team. A submissive chameleon will signal its defeat by flooding its skin with melanin pigments and turning a dull brown color.

The finesse of a fully developed upper cell layer is the province of adult male panther chameleons. All others have the second layer of more loosely organized photonic crystal cells—known as iridophores—that reflects light on a wider gamut.

“These cells, which contain larger and less ordered crystals, reflect a substantial proportion of the infrared wavelengths,” Michel Milinkovitch, one of the study authors, reported in a press release.

Because the gamut includes this infrared light (invisible to humans), which nears the heat wave segment of the spectrum, scientists have suggested that the deeper iridophores can aid cold-blooded animals with temperature regulation, according to Drake. Though it is now clear that crystals are the mechanism for chameleon color change, scientists aren’t sure how the animals are able to control them so precisely.

“Even though chameleons have attracted attention for centuries, there’s still a lot of mystery surrounding them,” Christopher Anderson, a chameleon expert at Brown University, told National Geographic’s Patricia Edmonds. “We’re still piecing together how their mechanisms actually work.”

There are over 200 documented species of chameleon. However, that number is dwindling: Edmonds reports that the International Union for Conservation of Nature (IUCN) has listed nine species as critically endangered, 37 as endangered, 20 as vulnerable and 35 as near-threatened. The animals remain an intriguing facet of study, though, and are inspiring developments of human technologies as well.

While Milinkovitch and his team continue to study the workings of chameleons, other researchers are working to apply their knowledge of nanocrystalline structures to create long-lasting color in textiles and paints, according to Drake.