The unique behavior of compounds confined at interfaces can be very different from those in bulk situations. Determining structure and chemical bonding at surfaces is central to continued progress in the field, and there are several questions yet to be answered: how can chemical reactivity be optimised for selective and efficient processes? How reliable are methods for determining molecular conformation at surfaces? How can the diffusion of molecules at surfaces be controlled in order to influence growth? This Faraday Discussion focusses on understanding the interaction of molecules with surfaces and their subsequent organisation, reactivity, or properties from both experimental and theoretical perspectives. It features contributions from scientists working on surface structuring with molecules, surface reactivity, characterisation, measurement of properties and modelling all of these features.