To understand the development of science-related thinking, acting, and learning in middle childhood, I studied youth in schools, homes, and other neighborhood settings over a three-year period. The research goal was to analyze how multiple everyday experiences influence children's participation in science-related practices and their thinking about science and scientists. Ethnographic and interaction analysis methodologies were to study the cognition and social interactions of the children as they participated in activities with peers, family, and teachers (n=128). Interviews and participant self-documentation protocols elucidated the participants' understandings of science. An Everyday Expertise (Bell et al., 2006) theoretical framework was employed to study the development of science understandings on three analytical planes: individual learner, social groups, and societal/community resources. Findings came from a cross-case analysis of urban science learners and from two within-case analyses of girls' science-related practices as they transitioned from elementary to middle school. Results included: (1) children participated actively in science across settings—including in their homes as well as in schools, (2) children's interests in science were not always aligned to the school science content, pedagogy, or school structures for participation, yet children found ways to engage with science despite these differences through crafting multiple pathways into science, (3) urban parents were active supporters of STEM-related learning environments through brokering access to social and material resources, (4) the youth often found science in their daily activities that formal education did not make use of, and (5) children's involvement with science-related practices can be developed into design principles to reach youth in culturally relevant ways.