Attachment theory and research have emphasized the importance of understanding the individual as existing withing a network of relationships. The idea of development being relationship based, and interactions with the primary caretaker leading toward the internalization of a relationship experience, is quite different from and complements psychoanalytic ideas about development. In this article, attachment as a relationship approach for understanding development is contrasted with relevant psychoanalytic perspectives. Current theoretical and research concepts focusing on affect development and the evolution of the parent–infant relationship are discussed. A broader understanding of attachment is presented, which includes two ideas. The first is that internal representations build on internal working models of development. The second is that the attachment concept, combined with systems theory, is a way to conceptualize aspects of family theory and therapy. Finally, clinical implications of attachment theory and research are discussed.