First transition children go through from family to the nursery or kindergarten and/or from preschool to elementary school is the most significant period in the lives of children, but at the same time the most challenging ones. Although they are actually learning situations and provide children with opportunities to develop new roles and coping strategies for adapting and dealing with a new environment/rules/people; children, parents, and teachers also very often perceive them as stressful. In order to explore the sources of transition-related stress and the protective factors during children's transitions, it is important to examine significant determinants of children's educational transitions postulated within the contemporary Ecological-dynamic model of transition. This is the main goal of the research project „Children's well-being in transition periods: The empirical validation of the Ecological-Dynamic model“, which has been running since 2018 and is supported by the University of Rijeka, Croatia. In addition to presenting this theoretical model, this paper will include an overview of some research studies conducted within the project, key findings, and future directions in the area of teacher-child relationships, attachment development during transitions, socio-emotional well-being during transitions, transition objects, transition of different children, and different transition practices. In addition, this review aims to highlight some important issues related to transitions in childhood and provide the guidelines for improving transition practices and future research.