Research has shown that one of the factors that enable effective teachers is their rich "Pedagogical Content Knowledge" (PCK), a special blend of content knowledge and pedagogical knowledge that is built up over time and experience. This form of professional knowledge, first theorized by Shulman (1987), is topic-specific, unique to each teacher, and can only be gained through teaching practice. The academic construct of PCK is recognition that teaching is not simply the transmission of concepts and skills from teacher to students but rather a complex and problematic activity that requires many and varied on the spot decisions and responses to students' ongoing learning needs. This research addresses the key area of early career teacher education and aims to investigate the use of a "Content Representation" (CoRe) as a planning tool to develop early career secondary teacher PCK. The study is designed to examine whether such a tool, co-designed by an early career teacher (ECT) with expert content and pedagogy specialists, can enhance the PCK of early career science and technology secondary teachers. The content and pedagogy experts generally worked constructively with the ECTs in designing their CoRes. The ECTs noted that they highly valued the input of the experts and felt that the design process had enabled them to identify and access the knowledge about the key concepts of the topic, as well as learn new pedagogical techniques for delivering particular content material. All the ECTs reported that they felt that being involved in discussions with the experts in the construction of the CoRe helped them to understand the big picture of the topic. Although the teachers kept in mind the needs of the curriculum and assessment through these discussions, they felt that the CoRe discussions were somewhat liberating in allowing exploration of what the topic itself was all about. (Contains 2 tables and 1 figure.)