This book gives an account of state-of-the-art investigations of properties and processes at solid-liquid interfaces with the same precision as is standard in ultrahigh-vacuum-based surface science. Using combinations of in situ and ex situ experimental methods, fundamental and relevant phenomena such as adsorption and desorption of ions and molecules, restructuring of surfaces, thin film and nanocluster growth, and electrochemical reactions on the micrometer scale are addressed. The overview includes a wide range of experimental techniques and examples of solid-liquid interfaces and aims at stimulating an expansion of this important type of interface science.