This paper explores how a group of pre-service elementary science student teachers came to understand the development of their Pedagogical Content Knowledge (PCK) over the course of a semestera??s study in a science methods course. At the start of the semester, PCK was introduced to them as an academic construct and as a conceptual tool that they could use to plan for, and assess, the development of their professional knowledge and practice as beginning science teachers. All participants were provided with a tool known as a CoRe (Content Representation) and the manner in which they worked with the CoRe was such that it supported them in planning for and assessing their own learning about teaching elementary science through a focus on the development of their PCK. Through analysis of data derived from the application of a CoRe based methodology (modified and adapted for this study) to the teaching of the science topic of Air, participantsa?? reasons for, confidence in, and perceived meaningfulness of their learning about science teaching could be examined. In so doing, the nature of participantsa?? PCK development over time was made explicit. The results illustrate real possibilities for ways of enhancing student teachersa?? ongoing professional learning in teacher preparation and offer a window into how the nature of PCK in pre-service education might be better understood and developed.