Social and developmental psychology are often viewed as distinct subdisciplines, each with its own theories and methodologies. However, this book seeks to bridge that divide by proposing an integrative framework that considers various levels of analysis, from the individual to the societal. It emphasizes the interplay of fundamental concepts such as intra- and inter-group conflict and change across these levels. By revisiting and renewing foundational theories of development, the book introduces the concept of 'genetic social psychology.' This approach is applied to the complex case of the Cyprus conflict, as well as other conflict and post-conflict scenarios, uncovering transformative possibilities for both theory and practice. Ultimately, this work advocates for a broader, more cohesive understanding of psychological processes in social contexts, addressing contemporary challenges and enhancing our grasp of human behavior.