This paper considers the tacit dimension of teaching. Policy and research focused on teaching have addressed the explicit application of knowledge within the field. This paper views knowledge from the positions of explicit knowledge, and implicit or tacit knowledge. Although widely acknowledged as a contributing constituent of teachers' practice, there has been limited research on tacit knowledge in teaching. The nature of teachers' work generates evidence from observable behaviour and action, and has contributed significantly to contemporary research on practice. Where there is a gap in similar expanse of research is on the understanding of the non-observables and implicit or tacit knowledge which informs practice. This area of tacit knowledge in teaching remains minimally understood and under-researched. The research presented in this paper identifies underlying cognitive processes which inform practice in teaching. For the first time in research on teaching, these cognitive processes have been amalgamated to capture what happens beyond that which is observable. A call for unison on the dynamics of implicit and explicit knowledge in teaching is urgent to unearth complexity and externalise professional development stages. The findings from this paper will be beneficial to teachers, teacher educators and policymakers.