Chameleon turquoise, and purple. Chameleon skin has a superficial layer which contains pigments, and under the layer are cells with guanine crystals. Chameleons change colour by changing the space between the guanine crystals, which changes the wavelength of light reflected off the crystals which changes the colour of the skin. Colour change in chameleons has functions in camouflage, but most commonly in social signaling and in reactions to temperature and other conditions. The relative importance of these functions varies with the circumstances, as well as the species. Colour change signals a chameleon's physiological condition and intentions to other chameleons. Chameleons tend
Military camouflage unit, the first of its kind in any army. He also invented painted canvas netting to hide machine gun positions, and this was quickly taken up for hiding equipment and gun positions from 1917, 7 million square yards being used by the end of the war. The First World War also saw the birth of aerial warfare, and with it the need not only to conceal positions and vehicles from being spotted from the air, but also the need to camouflage the aircraft themselves. In 1917, Germany started using a lozenge camouflage covering Central Powers aircraft, possibly the earliest printed