Introduction to the methodology of the study: Grasping the multilinear and unique developmental process over time

This chapter introduces the research methodology. To investigate the dynamics of professional identity construction, a qualitative approach was selected, and in accordance with the Trajectory Equifinality Model, historically structured sampling was applied. The following methods were included in the research: interviews, questionnaires, essays, and the Double Direction Theme Completion (DDTC) method. The DDTC method was developed to map the dynamics of the coordination of different sub-systems in the self.