The article investigates the mechanism behind the rapid and complex color changes observed in chameleons, particularly the panther chameleon. Using microscopy, photometric videography, and photonic band-gap modeling, the researchers found that chameleons change color by actively tuning the lattice of guanine nanocrystals within a superficial layer of dermal iridophores. This active tuning shifts the color from blue to yellow/orange, while a deeper layer of iridophores with larger crystals reflects sunlight, especially in the near-infrared range. The combination of these two layers allows chameleons to combine efficient camouflage with dramatic displays and potentially provides thermal protection. The study also highlights the evolutionary novelty of this two-layer structure in chameleons, which may have evolved to enhance survival in open, sunny environments.The article investigates the mechanism behind the rapid and complex color changes observed in chameleons, particularly the panther chameleon. Using microscopy, photometric videography, and photonic band-gap modeling, the researchers found that chameleons change color by actively tuning the lattice of guanine nanocrystals within a superficial layer of dermal iridophores. This active tuning shifts the color from blue to yellow/orange, while a deeper layer of iridophores with larger crystals reflects sunlight, especially in the near-infrared range. The combination of these two layers allows chameleons to combine efficient camouflage with dramatic displays and potentially provides thermal protection. The study also highlights the evolutionary novelty of this two-layer structure in chameleons, which may have evolved to enhance survival in open, sunny environments.