Although interest has been repeatedly identified as a powerful basis for learning and academic achievement, limited empirical work has looked at the structural composition, persistence, stability, and development of interests over time. Such work is necessary to support developmental models of interest empirically. Using 6 dimensions identified in literature as underlying the development of interests (time, value, agency, frequency, intensity, and mastery), the 7,226 interests of 204 Dutch high school students were explored by examining the structure of these dimensions over time. To measure students' multiple interests and their development across contexts and over time, we used experience-sampling methodology through a smartphone application at 2 time points, 3 months apart. Using cross-sectional latent profile analyses, we found that the data best supported 2 nearly identical sets of 6 profiles at both time points. These profiles, consisting of both homogeneous (i.e., similar scores on all dimensions) and heterogeneous (i.e., characterized by interactions across dimensions) patterns of scores across the dimensions, were then investigated longitudinally to evaluate them within developmental theory. The structures of the profiles and the transitions between profiles over time largely align with common descriptions of interest development. However, discrepancies hinting at a novel and separate developmental trajectory were found, requiring further investigation.