The platform economy is growing rapidly. More and more Software Ecosystems are emerging. As a result, several companies are faced with the question of how they can build up and establish an ecosystem. Software Ecosystems are much more complex than software systems. The technological, business and legal implications are far more difficult to understand if products and services have to be designed across companies. In more than 20 ecosystem projects, we have repeatedly encountered challenges in the conception and modelling of such ecosystems. This leads us to develop a method, the so called "Tangible Ecosystem Design“, that promotes the cooperation between stakeholders in the definition, design and analysis of a Software Ecosystem with the help of Playmobil® toys in an workshop context. In this contribution, we present the method and discuss our findings and experiences in the application in real world projects.