Adsorption and self-organization of organic molecules on solid substrates have been studied extensively in vacuum and at solid–liquid interfaces. Under electrochemical conditions, however, an often exceptional level of control over adsorption and self-organization can be achieved. The source of this control lies in modulating the strength of the interactions between adsorbates, substrate, and electrolyte through the electric field at the electrode–electrolyte interface and has both thermodynamic and kinetic origins and implications. This article briefly introduces the most important substrates for studying adsorption and self-organization under electrochemical control and the main techniques used. We then discuss the principles responsible for switching and tuning supramolecular structures under electrochemical control, by analyzing representative examples.