Emotions are generated and regulated in the context of close relationships, such as mother-child relationships. Children's emotional development is primarily directed by mother-child emotional processes. In the current review, we examine the advances in understanding how mother-child relationships impact emotion development. In particular, we explore novel and advanced techniques in measurement and design, autonomic psychophysiology, the structure of emotion socialization, and modeling of parent-child dynamics. As these innovations continue to progress, we expect that theoretical models of emotional development will be further refined.