The field of Didactique is rich, deep and extensive. To a large extent, it owes its shape and even its existence to the energy and inspiration poured in by Guy Brousseau starting in the 1960's. Many others have since added their ideas and energies to produce a unique, vibrant, multi-faceted research program. Invitation to Didactique provides an easily accessible general introduction to the field, hitting the high spots and focusing largely on the contributions of Brousseau himself. Teaching Fractions through Situations: a Fundamental Experiment takes one fundamental aspect and examines it in a great deal more depth from several perspectives. It gives a detailed description of a particularly interesting way of teaching fractions and decimals which should be interesting to any reader who enjoys seeing children learn mathematics. It then examines two other aspects of the lesson sequence, first describing the exciting and challenging role of the teachers handling a highly unfamiliar approach and then placing the whole experience in its context in the very earliest phases of the development of this very important field of research.