This volume is dedicated to the memory of Issai Schur. It opens with some biographical reminiscences of the famous school he established in Berlin, his brutal dismissal by the Nazi regime and his tragic end in Palestine. This is followed by an extensive review of the extraordinary impact of his lesser known analytic work. Finally, leading mathematicians in the representation theory of the symmetric groups, of semisimple and affine Lie algebras and of Chevalley groups have contributed original and outstanding articles. These concern many areas inspired by Schur's work as well as more recent developments involving crystal and canonical bases, Hecke algebras, and the geometric approach linking orbits to representations. Contributors: Biography: H. Abelin-Schur, W. Ledermann, Y. Ne'eman,B. Neumann, P.M. Neumann, M. Sonis. Review: H. Dym, V. Katsnelson. Original papers: H.H. Andersen, A. Braverman, S. Donkin, V. Ivanov, D. Kazhdan, B. Kostant, A. Lascoux, N. Lauritzen, B. Leclerc, P. Littelmann, G. Luzstig, O. Mathieu, M. Nazarov, G. Olshanski, E. Opdam, A. Regev, M. Reineke, C.S. Seshadri, J.-Y. Thibon, M. Varagnolo, E. Vasserot, A. Vershik. The first part of this book will appeal to a general audience. The second part will be of interest to graduate students especially those in analysis, while the third part is addressed to specialists in Lie algebras.