Cytokinins are hormones involved in all aspects of plant growth and development and are essential for in vitro manipulation of plant cells and tissues. Much information has been gathered regarding the chemistry and biology of cytokinins, while recent studies have focused on the genetics and cytokinin-related genes. However, other than proceedings of symposia, no single volume on cytokinins has been written. This book is the first of its kind, homing in on the key subject areas of cytokinin-chemistry, biosynthesis, metabolism, activity, function, genetics, and analyses. These areas are comprehensively reviewed in individual chapters by experts currently active in the field. In addition, a personal history on the discovery of cytokinin is presented by Professor Folke Skoog. This volume summarizes previous findings and identifies future research directions.