Plant hormones play a crucial role in controlling the way in which plants growand develop. Whilemetabolism providesthepowerand buildingblocks for plant life, it is the hormones that regulate the speed of growth of the individual parts and integrate these parts to produce the form that we recognize as a plant. In addition, theyplayacontrolling role inthe processes of reproduction. This book is a description of these natural chemicals: how they are synthesizedand metabolized; howthey work; whatwe knowof their molecular biology; how we measure them; and a description ofsome of the roles they play in regulating plant growth and development. Emphasis has also been placed on the new findings on plant hormones deriving from the expanding use ofmolecular biology as a tool to understand these fascinating regulatory molecules. Even at the present time, when the role of genes in regulating all aspects of growth and development is considered of prime importance, it is still clear that the path of development is nonetheless very much under hormonal control, either via changes in hormone levels in response to changes in gene transcription, or with the hormones themselves as regulators ofgene transcription. This is not a conference proceedings, but a selected collection ofnewly written, integrated, illustrated reviews describing our knowledge of plant hormones, and the experimental work that is the foundation of this knowledge.