Purpose: The aim of this paper is to describe teachers' professional development in Lesson Study (LS) as processes situated in Semiosphere and generated by the unevenness due to different cultural traditions. The authors characterise teachers' professional development in two LS experiments as processes generating new knowledge to point out their products, i.e. new professional frame teachers produce after these experiments. The authors use Hybridization, a particular form of Networking of Theories (NWT). Design/methodology/approach: The authors collected video-registration of several Italian LS meetings. The authors analyse two LSs, where time emerged as a conflictual aspect. Through Hybridization components, the authors show how teachers make sense of LS and how teachers revise their professional frame. Theoretical framework: In NWT different theories are deployed to study the same problem. To grasp the issue of unevenness in our LS, we use "Hybridization of a Theory," a form of NWT characterised by a structural asymmetry. It is given when a construct "c" is introduced "coherently, operatively and productively" into a theory T, obtaining a hybridized "theory" T'. Findings: Hybridization lens allows to describe potentialities and limits of LS as a tool for teachers' development. The two analysed LS are different: in one of them Hybridization process produced a new theory T', whilst in the second one it was limited to the awareness of a gap between LS and initial teachers' professional frame. Practical implications: Identifying links between different Hybridization components is a helpful tool for teacher educators/researchers to foster the shift from one another. For instance, through this tool, teacher educators could keep track of what happens in successive LS and mirror the dialogue between teachers, moving towards group-shared metareflections. This initiates the advancement of a new theory T', where asymmetries are interpreted. Originality/value: In this approach teachers are protagonists of the construction of a new professional frame. LS is a tool for teachers' professional development, allowing teachers to question their own educational intentionalities. Hybridization components provide a tool to analyse such a process.