In this volume we have attempted to present a concise survey of the spectroscopic properties of insulators as derived from the application of tunable laser spectro?? scopic techniques. As has been the case in gaseous atomic spectroscopy, the use of tunable lasers has allowed the extension and the refmement of optical measure?? ments in the condensed phases to unprecedented resolutions in the frequency and temporal domains. In turn, this firmer base of empirical fmdings has led to a more sophisticated theoretical understanding of the spectroscopy of optically excited states with major modifications being apparent in the area of their dynamic be?? havior. Yet the revivalistic nature of these advances implies that additional advan?? ces are to be expected as the techniques and developments outlined in this volume are put to widespread use. Regardless, it is our hope and that of our distinguished colleagues in this venture that the reviews presented here will be useful to neo?? phytes and veterans to this field alike - to the former as a laissez-passer into solid-state spectroscopy, to the latter as a useful synopsis and reference of recent developments. We have also attempted to expose the reader to the concept that optically active materials, be they organic or inorganic, as universality would require, be?? have in a like manner and, though terminology may vary in detail, the outline and general features of all insulators remain constant.