Understanding important scientific concepts like matter, energy, force, and species is central to scientific literacy. But how do we learn scientific concepts? This book explains what research across distinct theoretical perspectives has taught us and then cuts through the diversity to offer a novel integrated account and a unified theory of conceptual change. Theoretical perspectives from science education, cognitive science, developmental psychology, the learning sciences, and the history and philosophy of science are often seen as competing alternatives and practical pedagogical recommendations diverge, sometimes even contradicting one another. Learning Scientific Concepts responds by explaining and evaluating prominent theoretical perspectives: the nature of concepts and conceptual development, in general, as understood in cognitive and developmental psychology; and theory change, knowledge-in-pieces, and situated/embodied/distributed perspectives on science concept learning, in particular. It then integrates these perspectives and proposes the Unified Theory of Conceptual Change (UTCC), building on Susan Carey’s foundational account of concepts and conceptual development in developmental psychology and Edwin Hutchins’ multilevel approach to analyzing cognitive systems in cognitive anthropology. The UTCC outlines a comprehensive modeling toolkit for making sense of how we learn scientific concepts at different levels of analysis. This book serves as a comprehensive guide for researchers, advanced students, and practitioners to the most important research on learning scientific concepts. In proposing a novel theoretical synthesis, it also suggests a way forward for researchers and offers practitioners a coherent and comprehensive story of what kind of instruction and curricular design is effective and why.