The book's primary intention is to serve as a roadmap for professionals working in developing countries interested in the Nexus Water-Energy-Food-Ecosystems (WEFE) approach. The book shows a multi-disciplinary approach, showcasing the importance of the proper use of Nexus WEFE when implementing certain development programs in regions around the globe. It can be presented as a manual for an individual that either wishes to implement intervention projects following the NEXUS approach or students interested in cooperation and development. The book begins with a general explanation of the theoretical concepts and implementation processes of Nexus WEFE and continues getting into case studies, explaining the importance of proper implementation and potential drawbacks and solutions to them. This book has a particular focus on the European Union cooperation policies when implementing such an approach in developing countries.