Trees are important in both natural populations as native forests and for their commodity value in the production of forest products. Thus, the most important reason to study forest genetics is to provide insight into the evolution, conservation, management and sustainability of the world's natural and managed forests. For this reason, the intention of this book is to describe concepts and applications of forest genetics in all types of forests ranging from pristine natural forests to monoculture plantations. It is aimed at several audiences: as a first course text for advanced undergraduate and graduate students; a reference for professionals and researchers in forestry; and an introduction for scientists interested in other sub-disciplines of forest genetics. No previous knowledge of genetics is assumed.