False-colour scanning electron micrograph of the surface of a compact disc cracked to show the musical layer below (green). The disc is made of plastic, which is pressed with a series of fine depressions (yellow/red dashes) representing a digitised musical signal capable of being read by a laser. To reflect the laser light, the music layer is coated with a fine film of metal (unseen) which follows the depressions exactly. This layer is covered by another layer of transparent plastic (blue). The music is sandwiched between two layers of plastic, which prevents dust & scratches from affecting the sound. Magnification: x1500 at 6x4.5cm size.