The following article is based on a presentation given as part of Symposium X—Frontiers of Materials Research on December 4, 2002, at the 2002 Materials Research Society Fall Meeting. The cinema is just over 100 years old. From the beginning of motion pictures in the mid-1890s, the materials used for films have been at the heart of cinema technology. The material first used was cellulose nitrate film—unrivaled in its mechanical, physical, and aesthetic qualities, and also dangerously flammable. In the 1950s, cellulose nitrate was replaced, for safety reasons, by cellulose triacetate. Today, polyester film is widely used; nevertheless, the fact remains that the majority of the world's film heritage exists on two main material formats, cellulose nitrate and cellulose triacetate, both of which decay over time. Film archivists are engaged in a race to save historic film footage from being lost forever. Digital technology, now widely used in cinema, does not resolve the issue of the long-term preservation of films because digital formats are still evolving. This article discusses the materials used in motion-picture technology over the years, the mechanisms active in film decomposition, and international efforts to preserve and restore historic films.