This volume brings together leading investigators who integrate two distinct research domains in social psychology–people’s internal worlds and their close relationships. Contributors present compelling findings on the bidirectional interplay between internal processes, such as self-esteem and self-regulation, and relationship processes, such as how positively partners view each other, whether they are dependent on each other, and the level of excitement in the relationship. Methodological challenges inherent in studying these complex issues are described in depth, as are implications for understanding broader aspects of psychological functioning and well-being.