Instead of pits, CD-Rs (Compact Disc-Recordable) have a layer of bluish photosensitive organic dye, which is backed by a very thin reflective layer usually made of gold. When struck by a strong laser beam, the photosensitive dye absorbs light, heating the reflective layer in a localized pattern, and causing deformations in the reflective layer. This is why the phrase "burning a CD-R" is used, since laser light is used to burn data into the dye and reflective layers. The variations in reflectivity caused by such burning of data onto a CD-R are equivalent to the pits of CDs.