A film of molecules on a surface that can contain multiple layers of film. A Langmuir–Blodgett film with multiple layers can be made by dipping a plate into a liquid so that it is covered by a monolayer and then repeating the process. This process, called the Langmuir–Blodgett technique, enables a multilayer to be built up, one monolayer at a time. Langmuir–Blodgett films have many potential practical applications, including insulation for optical and semiconductor devices and selective membranes in biotechnology. These films are named after Irving Langmuir and Katharine Blodgett (1898–1979), who worked on them in the 1920s and 1930s.