Van der Waals' famous thesis on the study of intermolecular forces is now more than hundred years old. Important developments of our knowledge in this field, especially in the case of the hydrogen bond, have been obtained both from theoretical and experimental research. Hydrogen bonds exert a profound influence on all physical and chemical properties of the materials where they are formed. This book stems from an Erasmus course at the University of Leuven, Belgium on this topic together with supplementary articles.