This study is aimed at understanding the identity formation of pre-service science teachers (PST?s) who are transitioning from students to teachers and from science/engineering majors to education majors. This was done using the conceptual lens of identity within a specific socio-cultural context. The participants were three undergraduate students in their mid- to late twenties who had transferred to science education from natural science or engineering majors. Collection of data included in-depth interviews, story timelines, e-mail surveys, and participant drawings. The study revealed that the PST?s' identity formation was not one common universal process; rather, each person's experiences were individually affected positively or negatively by their life history. Although the three PST?s came from very similar social backgrounds in Korea, their identity formation was categorized into three different types: determined effort, critical exploration, and continuous confusion. This research shows that the life history model of PST?s' identity formation can be based on the individual and practical support to reduce the gap between the actual self and future self within science education.