Monolayers of molecules can be formed at a variety of interfaces, and over the years many techniques have been developed to construct them and to study the resulting organisation of the molecules.At a liquid-solid interface, 2D assemblies can be created by depositing a solution of the compound of interest on top of the substrate.Depending on the nature of the solvent, the substrate, and the dissolved molecules, the latter might form an ordered monolayer at the liquid-solid interface.When the interactions remain relatively weak, the process is called physisorption.Advanced interface specific methods such as scanning tunneling microscopy (STM) are needed to study the interface at the nanoscopic level.[1]