The overarching goal of this book volume is to illuminate how research on science teacher identity has deepened and complicated our understanding of the role of identity in examining teacher learning and development. The collective chapters, both theoretical and empirical, present an array of conceptual underpinnings that have been used to frame science teacher identity, document the various methodological approaches that researchers have implemented in order to study science teacher identity within various contexts, and offer empirical evidence about science teacher identity development. The findings of the studies presented in this volume support the argument that teacher identity is a dynamic, multidimensional and comprehensive construct, which provides a powerful lens for studying science teacher learning and development for various reasons. First, it pushes our boundaries by extending our definitions of science teacher learning and development as it proposes new ways of conceptualizing the processes of becoming a science teacher. Second, it emphasizes the role of the context on science teacher learning and development and pays attention to the experiences that teachers have as members of various communities. Third, it allows us to examine the impact of various sub-identities, personal histories, emotions, and social markers, such as ethnicity, race, and class, on science teachers’ identity development. The book aims at making a unique and deeply critical contribution to notions around science teacher identity by proposing fresh theoretical perspectives, providing empirical evidence about identity development, offering a set of implications for science teacher preparation, and recommending directions for future research.