This book provides a comprehensive study of the symmetry and geometry of crystals and molecules, starting from first principles. The pre-knowledge assumed is mathematics and physical science to about A-level; additional mathematical topics are discussed in appendices. It is copiouslyillustrated, including many stereoviews, with instructions both for stereoviewing and for constructing a stereoviewer. Problems for each chapter are provided, with fully worked tutorial solutions. A suite of associated computer programs has been devised and placed on-line, for assisting both thestudy of the text and the solutions of the problems. The programs are easily executed, and instructions are provided in the text and on the monitor screen. The applicability of symmetry in everyday life as well as in science is stressed. Point groups and space groups are first discussed and derivedin a semi-analytical manner, and later by use of group theory. The basic principles of group theory are discussed, together with applications to symmetry, chemical bonding and aspects of vibrations of molecules and crystals. The book is addressed to those studying the physical sciences and meeting the subject for the first time, and it brings the reader to a level of appreciation for the definitive works produced by the International Union of Crystallography, such as the International Tables for X-ray Crystallography,Vol 1 (1965) and the International Tables for Crystallography, Vol A (2006).