This guidebook was developed as part of the "Transition Is Our Mission" (TIM) project, aimed at ensuring a smooth transition for children from preschool to primary school. The document provides research-based insights and practical tools for educators and other stakeholders involved in this transition, focusing on developmental, pedagogical, and professional continuity. It includes guidelines and examples of good practices from Croatia, Latvia, and Slovenia, addressing challenges such as ensuring consistency in teaching approaches and providing support to families. The guidebook's main goal is to help schools and preschools create a supportive, child-centered transition that enhances both academic and social outcomes. The resource is inspiring due to its cross-country collaboration and emphasis on inclusive education for all children, including those from vulnerable backgrounds.