Langmuir films are thin layers of molecules that form at the air-water interface. They are created by spreading a monolayer of amphiphilic molecules, which have both hydrophilic (water-attracting) and hydrophobic (water-repelling) parts, on the surface of water. This arrangement allows the molecules to align themselves, creating a stable film that can be studied for various properties. These films are important in fields like material science and biophysics because they can mimic biological membranes and help researchers understand molecular interactions. Langmuir films are also used in the development of new materials and coatings, making them valuable in both research and industrial applications.