In this chapter, the authors aim at theoretically developing the TPCK framework toward a process-oriented model of teachers’ pedagogical reasoning about technology. To address this issue, they elaborate on the transformative view of TPCK, introducing the notion of mental models, as analogue and continuous knowledge representations (Johnson-Laird PN, Cogn Sci 4:71–115, 1980). Based on this, they propose two levels of cognitive transformation. First, they claim that the cognitive transformation of knowledge in the basic sub-domains (TK, PK, CK) into knowledge in the intersecting sub-domains (PCK, TPK, TCK) can be defined as the construction of mental models. Second, regarding TPCK as a construct, namely, the construction of knowledge supposedly integrating all sub-domains, they claim that TPCK can be conceptualized as meta-conceptual awareness of the demands of the teaching task, the teachers’ knowledge in the sub-domains and the respective context. These claims are discussed in terms of the background of coherent versus fragmented theories, based on the conceptual change literature.