The following chapter presents the basics of ellipsometry and discusses some recent advances. The article covers the formalism and theory used for data analysis as well as instrumentation. The treatment is also designed to familiarize newcomers to this ßeld. The experimental focus is on adsorption layers at the air-water and oil-water interface. Selected examples are discussed to illustrate the potential as well as the limits of this technique. The authors hope, that this article contributes to a wider use of this technique in the colloidal physics and chemistry community. Many problems in our ßeld of science can be tackled with this technique. 組合式多功能橢偏儀