Knowledge about categories supports learning andgeneralization, and this knowledge is particularly importantearly in development. Although most theories of categoryknowledge posit a role for experience in acquiring thisknowledge, the current evidence for the presumed role ofexperience in category knowledge acquisition remains limitedto correlational evidence, indirect measures of categoryknowledge, and computational studies. Here we providedirect evidence that repeated experience with a biologicaldomain in an ecologically-valid setting changed children’scategory representations, with increased differentiation ofitems within that domain and relative to a second domain. Theimplications of these results for understanding the role ofexperience in category acquisition, and the contribution ofenrichment experiences to school readiness are discussed.