The first edition of this book provided an introduction to the many static and dynamic features of magnetic flux structures in what are now called classical or low-temperature superconductors. It went out of print not long after the discovery of high-temperature superconductors in 1986 by J.G. Bednorz and K.A. Miiller, a discovery which resulted worldwide in an explosive growth of research and development in the field of superconductivity. Because of this upsurge of activities, a strong demand for this book clearly continued. Since the contents of the fourteen chapters of the first edition are still valid and continue to represent a useful introduction into the various subjects, it was felt that a reprinting of these chapters in this second edition would be highly attractive. In this way, the reader is also able to trace the earlier scienti­ fic developments, themselves constituting important ideas sometimes forgot­ ten by the new community dealing with high-temperature superconductivity. However, because of the exciting and important recent progress in the field of high-temperature superconductivity, an extensive chapter has been added in this second edition. It provides a summary of the new developments and a discussion of the highlights. Here keywords such as vortex matter, vortex imaging, and half-integer magnetic flux quanta describe surprising new issues.