A natural phenomenon in cured meat (and some fresh meat) is the occurrence of iridescence or a rainbow appearance on the cut lean surface. Technically, this is referred to as birefringence. It is caused by the reflectance of light off of muscle proteins, and it is analogous to the color distribution produced by a prism. Muscle proteins are arranged in strands called myofilaments, which are bound together to form myofibrils. Myofibrils are bound together to form muscle fibers, which form together to form muscle bundles and finally whole muscles. When the myofilaments are cut at the appropriate angle, exposing a cross section of the myofilaments, the reflectance of light off the proteins produces the characteristic appearance associated with iridescence.