Partners combines in-depth interviews with quantitative data to show how innovations in the roles of graduate teaching assistants at universities are improving both their own experiences and the overall educational environment. This book addresses a topic of growing interest in higher education, namely the professional development of the future professorate. It explores the contribution that both undergraduate and graduate teaching assistants can play in undergraduate education, particularly in the sciences where considerable rethinking of both content and pedagogy is underway. Drawing on three studies of undergraduate reform initiatives-two in chemistry and one in astronomy-the author illustrates the under-used potential of teaching assistants as collaborators in implementing active and interactive models of teaching and learning. She points to unmet needs in the educational preparation and support of TAs in more traditionally-taught science courses, and the additional preparation that TAs require to be effective enablers of learning in support of new pedagogies. The TAs emerge from her studies as trouble-shooters, consultants, and collaborators in support of the innovations for which they work, with a potential for active collegial engagement that may be underestimated. They also provide insights into the causes of problems that undergraduates often experience in shifting to active learning modes, and of resistance to these changes among students, faculty, and TAs themselves.