Curiosity, interest, and intrinsic motivation are critical to the development of competence, knowledge, and expertise. Without a mechanism of intrinsic motivation, people would rarely explore new things, learn for its own sake, or engage with uncertain tasks despite feelings of confusion and anxiety. This article explores two sides of interest: momentary feelings (the emotion of interest) and enduring traits (the character strength of curiosity). Recent theories in emotion psychology can explain why and when people experience feelings of interest; recent research has illuminated the role of curiosity in cultivating knowledge, meaning in life, close relationships, and physical and mental resilience. The problem for future research – and for social and personality psychology more generally – is how to bridge the dynamics of everyday experience with stable, lifespan aspects of personality.