This dissertation investigates how teaching in a hands-on science center contributes to re/shaping one's teaching identity. Situated at the New York Hall of Science (NYHS) in Queens, New York, my research approach is to conduct a critical ethnography where the focus is on improving the teaching and learning of science for all involved. In particular, Explainers, floor staff at NYHS, who are studying to be science teachers, are invited to become co-researchers with me. Written as a manuscript style, this dissertation consists of six chapters. Each chapter foregrounds certain events and phenomena, and theory and method are woven in to theorize identity construction. Grounded in cultural sociology, the frameworks of Cultural Historical Activity Theory (CHAT), and the sociology of emotions, illuminate key understandings about the construction of teaching identity. Multiple data sources including field notes, transcribed audio and videotapes, and cogenerative dialogues are used. I employ a hermeneutic phenomenological approach to data analysis. This research has salient implications for museum-university partnerships, and training for museum floor staff and has the potential to inform policy-making for pre-service teaching clinical fieldwork experiences. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]