This book is designed to guide students through the latest developments of theory and research on relationships from adolescence to young adulthood. Unique to this text is a focus on relationship change across middle childhood into adolescence and across late adolescence into early adulthood. Experts on adolescent relationships from across the globe summarize the current state of literature on family and peer relationships, as well as the environmental and genetic factors that influence them. Students will benefit from the comprehensive, rigorous, yet accessible overview of key content; such as what defines the relationship processes, what describes the individual and contextual factors that influence relationships, family relationships, sibling relationships, and parent-child relationships during the transition into adolescence and into young adulthood.