Ordered systems exhibit physical properties and behavior unknown in media where structural ordering and organization do not take place. In ordered systems special correlations between molecules exist and the results are remarkable properties: the functional order of biological systems, the electrooptical and mechanical proper­ ties of liquid crystalline materials and stretched polymers are just a few examples. New methods and techniques in optical spectroscopy have recently been developed to study ordered systems and guest molecules. This stimulated the organization of a NATO Advanced Study Institute bringing together chemists and physicists from optical spectroscopy, materials science, and biology. Thereby a unifying and interdisciplinary survey of possible applications of spectroscopy with polarized light to ordered systems, such as liquid crystals, stretched polymers, polymeric liquid crystals, and membranes, was achieved. The interdisciplinary approach of the meeting is reflected in the book. Different aspects of the same topic are often treated in several chapters all through the book. Therefore, each reader should look for the contributions which serves his needs, even if this means that some chapters will be skipped. The Advanced Study Institute, "New Developments in Polarized Spectroscopy of Ordered Systems", was the first scientific event of the celebrations of the 900th anniversary of the University of Bologna. The international and multidisciplinary approach of this ASI well converged in the tradition of the "Studium" at Bologna.