Theories on children and adolescent emotion dynamics were reviewed using data from 102 ecological momentary assessment studies with 19,928 participants and 689 estimates. We examined age-graded differences in emotional intensity, variability, instability, inertia, differentiation, and augmentation/blunting. Outcomes included positive versus negative affect scales, discrete emotions (anger, sadness, anxiety, and happiness), and we compared samples of youth with or without mental or physiological problems. Multilevel models showed more variable positive affect and sadness in adolescents compared with children, and more intense negative affect. Our additional descriptive review suggests a decrease in instability of positive and negative emotions from early to late adolescence. Mental health problems were associated with more variable and less intense positive affect, and more intense anxiety and heightened sadness variability. These results suggest systematic changes in emotion dynamics throughout childhood and adolescence, but the supporting literature proved to be limited, fragmented, and based on heterogeneous concepts and methodology. (PsycInfo Database Record (c) 2022 APA, all rights reserved).