This dissertation reported three studies whose overarching purpose is to enhance our understanding about how teachers learn to teach by revealing the learning to teach process. Each of three studies revealed the learning to teach process from different perspectives. Guided by the Pedagogical Content Knowledge (PCK) framework, the first study revealed the learning process of elementary teachers' development of engineering PCK through engineering teaching practices. Approaching elementary teachers' learning to teach engineering from the perspectives of innovation adoption and expertise development, the second study revealed the learning to teach engineering process by constructing a framework depicting the stages and dimensions involved in the elementary engineering education (EEE) adoption process and the EEE expertise development process. A phenomenological approach was adopted in both the first and the second studies. The third study, using a two-phase explanatory sequential mixed methods research design, revealed the process of learning to teach with education technology during student teaching by showing how pre-service teachers' progress in readiness for technology integration was affected by various contextual- and personal-level factors. Each of the three studies contributes to our understanding of how teachers learn to teach through teaching practices. The learning to teach processes revealed in the three studies carry important implications for professional development and teacher preparation. [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/en-US/products/dissertations/individuals.shtml.]