This chapter is devoted to the properties of surfactants and of their dispersions. We first review the structural features of surfactants, based on the polar head groups that determine their phase behaviour and applications. The chapter particularly focuses on the self-assembly of nanostructures, especially for their usage in conservation science and for the formulation of nanostructured liquid systems. The environmental aspects related to the use and disposal of amphiphiles are discussed. The concluding section addresses the main experimental techniques that are currently used to investigate the physico-chemical properties of self-assemblies. The chapter is intended to provide the theoretical background as a support for the applications described in other parts of this book.