Caption:
Scanning electron microscope image of the lenticular array in the U.S. 100 dollar bill. The lenticular array, or micro-lens, shows a different colour when the viewing angle of the bill is changed. This is just one of the security (anti-counterfeit) features of the United States 100 dollar bill, others include: micro-print, watermarks, lenticular images, special inks, fluorescent fibers and strips, coloured fibers, and the use of full coloured inks.