Children's multiple interests intersect with their participation in informal learning practices in dynamic ways. Using a theoretical framework illustrating interest as a multifaceted construct that has different forms and a range of scope and durability, this study investigates how children's situational interests and individual interests are developed and reinforced and how they support micro-practices (i.e., any small practices, actions, activities, interactions that occur moment-by-moment) and vice versa. From a larger data set collected from one-time family science learning sessions at a museum, three children (aged 6-10) were strategically sampled to foreground an enhanced understanding of how interest and participation in practice mutually constitute each other. Using video-based interaction analysis, our case study of three children illustrates different patterns where micro-practices intersect with different types of interests at the museum. Even in the same environment with the same exhibits, each child from this case study constructed a unique pathway of forming the collection of micro-practices that was constantly interacting with situational interests and individual interests in specific disciplines, topics, exhibits, or any other various targets. For example, when having a strongly existing individual interest in a specific science discipline, one child's micro-practices were mainly driven by making choices of exhibits that are related to his science interest, while another child did not actively choose exhibits but found her own creative ways to connect her science interest and other new interests. Our study contributes to a more robust conception of interest that highlights the intertwining of multiple, malleable, and moment-by-moment interests and micro-practices in the museum.