Among the different players identified in the three layers of the framework, a central role is played by the communities that have been recognised especially in relation to the open innovation ecosystems. These communities can be composed of developers, enthusiasts, experts, or other stakeholders who share common interests or goals in the development of new ideas. Communities are the bedrock of bottom-up dynamics related to knowledge sharing and resulting in innovation based on informal institutions. As for the former element, communities often foster collaborative innovation by bringing together individuals with diverse skills and perspectives. They contribute to open-source software projects, but also open hardware and open data projects sharing knowledge, information and collectively solving problems. Here, the sustainability of ecosystems depends on the engagement and vitality of these communities, but also on the respect of these informal institutions keeping the communities alive and trustable. When communities are active and engaged, they contribute to the long-term health and growth of the open innovation ecosystem as a whole.