This book is tailored for professionals involved in organizational development, policymaking, and systemic problem-solving across complex social, ecological, digital, and organizational contexts. It introduces systems thinking as a practical framework for understanding interconnected challenges by focusing on patterns, feedback loops, and systemic structures rather than linear cause-and-effect relationships. It includes a historical review of systems theory and cybernetics during the socialist period in Eastern and Central Europe, offering insights into how these ideas interacted with political philosophies and governance paradigms in the region. This contextualization enriches the understanding of systemic approaches within socio-political frameworks unique to that region and era. Organized into three parts, the book begins with foundational theory, proceeds to practical analytical tools such as causal loop diagrams and systemic intervention mapping, and concludes with advanced applications integrating systems thinking with design thinking, adaptive leadership, and strategic planning in the context of uncertainty. Drawing on empirical cases and methodological rigor, the book equips professionals with systemic awareness and learning-based strategies that are essential for sustainable transformation and adaptive governance in dynamic, interconnected sectors. Its clear yet precise language ensures accessibility and relevance for practitioners seeking grounded, actionable insights informed by scientific evidence.