A solid-liquid interface is a unique environment for the construction of two-dimensional molecular assemblies as a bottom-up approach towards functional surfaces. Scanning tunneling microscopy (STM) has proven itself as an excellent tool to characterize such surfaces at the molecular level, by means of visualization. Many rules of design for surface, solvent and chemical structure of the adsorbants have been established, but methods to externally manipulate surface assemblies after their formation are still under development. This feature article deals with these manipulation methods at the solid-liquid interface and evaluates, at the molecular level, the effects of temperature variation, irradiation with light, applied electric or magnetic fields, mechanical manipulation with the STM tip, and shear flow of the liquid phase.