Traditionally, personality psychology has been understood as the study of stability in people’s dispositions. However, a different strand of personality research has highlighted the importance of acknowledging and explaining the meaningful intraindividual variation in human thoughts, feelings, and behavior across different contexts and time. The goal of this paper is to review this strand, highlight current research, and outline key questions for future research. We summarize historical perspectives on the dynamic processes underlying the emergence of personality within and across individuals (e.g. the pioneering theorizing of Allport; the person-situation debate), recent theoretical and empirical advances in incorporating dynamic processes into the definition and assessment of personality (e.g., the study of personality states; dynamic approaches to personality including Cognitive Affective Personality System [CAPS], Whole Trait Theory, the Knowledge-and-Appraisal Personality Architecture [KAPA] framework, and Nonlinear Interaction of Person and Situation [NIPS]), and new directions in current research (e.g. idiographic approaches; understanding variability in narrative identity). We end with suggestions for future research.