An innovative, fascinating approach to an in-depth-study of electrocyclic reactions, a special case of the pericyclic reaction class. Theoretical methods at four different levels, namely, orbital symmetry conservation, the frontier orbital approach, Moebius-Hueckel and more sophisticated quantum-chemical methods, are used for the mechanistic investigation of these so-called 'no-mechanism' reactions. Each chapter details the underlying physico-chemical principles in a simplified, easy-to-follow manner and discusses latest advances in the field. A deeper knowledge of quantum mechanics is not required. Computer aided lessons containing animated models visualize and, such way, help to understand even more difficult mechanisms.