Change is the sine qua non of emotion regulation (ER) and, thus, to understand ER we must analyze its temporal dynamics. Articles in the ER section of this special issue provide strong empirical evidence for the centrality of temporal dynamics in the development of ER on 3 levels: Rapid changes in spatial and temporal dynamics across multimodal systems underlying ER; more slowly emerging ER change over periods of time and development; and change in ER across contexts, including social interactions, culture, and coregulation in parent-child interactions. I describe how the articles by Guassi Moreira and colleagues (2019) and Lavelli and colleagues (2019) exemplify the methodological and conceptual focus on temporal dynamics. Taken together, the articles on ER demonstrate the importance of interweaving a microlevel focus on neural and biological development with a more macrolevel focus on the broader contexts of ER to advance the science of emotional development. (PsycINFO Database Record (c) 2019 APA, all rights reserved).