A thin film is a layer of material ranging from fractions of a nanometer (monolayer) to several micrometers in thickness. The controlled synthesis of materials as thin films (a process referred to as deposition) is a fundamental step in many applications. A familiar example is the household mirror, which typically has a thin metal coating on the back of a sheet of glass to form a reflective interface. The process of silvering was once commonly used to produce mirrors, while more recently the metal layer is deposited using techniques such as sputtering. Advances in thin film deposition techniques during the 20th century have enabled a wide range of technological breakthroughs in areas such as electronic semiconductor devices, LEDs, optical coatings such antireflective coatings), hard coatings on cutting tools, and for both energy generation (e.g.  thin film solar cells and storage (thin-film batteries). It is also being applied to pharmaceuticals, via thin-film drug delivery.

The 2006 cinéma vérité documentary film, Thin, directed by Lauren Greenfield and distributed by HBO, is an exploration of The Renfrew Center in Coconut Creek, Florida; a 40-bed residential facility for the treatment of women with eating disorders. The film mostly revolves around four women with anorexia nervosa and/or bulimia and their struggles for recovery. It premiered on HBO on November 14, 2006.