We have been gratified by the warm reception of our book, by reviewers, colleagues, and students alike. Our interest in the subject matter of this book has not decreased since its first appearance; on the contrary. The first and second editions envelop eight other symmetry-related books in the creation of which we have participated: I. Hargittai (ed.), Symmetry: Unifying Human Understanding, Pergamon Press, New York, 1986. I. Hargittai and B. K. Vainshtein (eds.), Crystal Symmetries. Shubnikov Centennial Papers, Pergamon Press, Oxford, 1988. M. Hargittai and I. Hargittai, Fedezziikf6l a szimmetri6t! (Discover Sym- try, in Hungarian), Tank6nyvkiad6, Budapest, 1989. I. Hargittai (ed.), Symmetry 2: Unifying Human Understanding, Pergamon Press, Oxford, 1989. I. Hargittai (ed.), Quasicrystals, Networks, and Molecules of Fivefold Sym- try, VCH, New York, 1990. I. Hargittai (ed.), Fivefold Symmetry, World Scientific, Singapore, 1992. I. Hargittai and C. A. Pickover (eds.), Spiral Symmetry, World Scientific, Singapore, 1992. I. Hargittai and M. Hargittai, Symmetry: A Unifying Concept, Shelter Publi- tions, Bolinas, California, 1994. We have also pursued our molecular structure research, and some books have appeared related to these activities: vi Preface to the Second Edition I. Hargittai and M. Hargittai (eds.), Stereochemical Applications of Gas-Phase Electron Diffraction, Parts A and B, VCH, New York, 1988. R. Gillespie and I. Hargittai, VSEPR Model of Molecular Geometry, Allyn and Bacon, Boston, 1991. A. Domenicano and I. Hargittai (eds.), Accurate Molecular Structures, Oxford University Press, Oxford, 1992.

Introduction. Simple and Combined Symmetries. Molecules: Shape and Geometry. Helpful Mathematical Tools. Molecular Vibrations. Electronic Structure of Atoms and Molecules. Chemical Reactions. Space-Group Symmetries. Symmetries in Crystals. Index.