The objective of this book is to describe how an out-of-the-box toolkit for experienced facilitators is developed, prototyped, and evaluated. This LEGO SERIOUS PLAY ® toolkit will support facilitators in guiding organizations’ representatives on their way to their business model (re)definition by fostering creative confidence and creating a shared understanding of business models and value propositions within organizations, be it non-for-profit associations or Fortune 500 enterprises. The author's goal is to contribute both to science and practice as outlined in the subsequent chapter on research methodology in detail. Furthermore, the objective is to generate an impact in terms of applied science while advancing the field of research. The significant gaps in research have been investigated. Based on the analysis of current research gaps, one leading research question has been formulated for this thesis. The central question investigated was the following: Can a shared understanding of business models and customer value propositions be improved through a Serious Play approach?