One hundred years ago, when Martinus W. Beijerinck in Delft and Friedrich Loeffler on Riems Island discovered a new class of infectious agents in plants and animals, a new discipline was born. This book, a compilation of papers written by well-recognized scientists, gives an impression of the early days, the pioneer period and the current state of virology. Recent developments and future perspectives of this discipline are sketched against a historic background. With contributions by A. Alcami, D. Baulcombe, F. Brown, L. W. Enquist, H. Feldmann, A. Garcia-Sastre, D. Griffiths, M. C. Horzinek, A. van Kammen, H.-D. Klenk, F. A. Murphy, T. Muster, R. O'Neill, P. Palese, C. Patience, R. Rott, H.- P. Schmiedebach, S. Schneider-Schaulies, G. L. Smith, J. A. Symons, Y. Takeuchi, V. ter Meulen, P. J. W. Venables, V. E. Volchkov, V. A. Volchkova, R. A. Weiss, W. Wittmann, H. Zheng