The present volume concentrates on catalyst surfaces. The interaction of adsorbed molecules, mostly on heterogenous catalysts, although some reference to model catalysts is also made, is discussed here. Vibrational (infrared and electron energy loss spectroscopies, magnetic resonances (nuclear and electron spin) and thermal desorption methods have been included in this latter category. The reader will find also a comparison of these well established methods with their recent developments which make them much more attractive. Therefore, researchers working in the catalysis field will find much to interest them in this book.