The current research is about the impact of the young STEM researchers and practitioners program implemented within the STEM: Integrated teaching project. The aim of the program is to incorporate STEM integrated teaching knowledge in the teacher preparation period. In this phenomenological study, we explored five pre-school teachers' program experiences and their STEM conceptions. Data were collected with semi-structured interviews, including questions about the impact and elements of the program and participants' STEM conceptions. Content analysis showed that awareness for STEM education, development of integrated teaching knowledge, and program elements were the emergent themes about the program experience. Teacher candidates responded to the models that include realworld problems and engineering as contexts as most desirable when shown STEM education models to understand their STEM conceptions. The young STEM researchers and practitioners program can be evaluated as a developing model to be incorporated into teacher education programs. Further research can explore how pre-service teachers form their STEM conceptions and develop their integrated teaching knowledge.