Progress in molecular structure research reflects progress in chemistry in many ways. Much of it is thus blended inseparably with the rest of chemistry. It appears to be prudent, however, to review the frontiers of this field from time to time. This may help the structural chemist to delineate the main thrusts of advances in this area of research. What is even more important though, these efforts may assist the rest of the chemists to learn about new possibilities in structural research. This "user-oriented" series will be reporting progress in structural studies, both methodological and interpretational. Structural chemists of excellence will be critically evaluating a field or direction including their own achievements, and charting expected developments.