The Community building concept gives guidance to the different stakeholder groups and offers ideas on how-to connect the various communities within the EO4AGRI stakeholder groups. Creating continuity and sustainability of the many communities within agriculture is a challenge. A particular challenge is to create a space for communication across the stakeholder groups so that unnecessary overlaps can be avoided, and synergies made fruitful. The Community building concept document contains descriptions of the stakeholder groups, identifies their challenges and interests as well as describe the different actors within the stakeholder communities. Existing communities within the stakeholder groups typically have well established activities. The concept takes this information as a starting point in order to be relevant and to engage the right actor addressing the pain point and interests at the highest granularity. The INSPIRE hackathon concept is a useful already established strategy to ensure continuity and sustainability of the results made by the participants and organizers prior to a hackathon event, but also the results from each of the events. It can be said that the INSPIRE hackathon is not an event, it is a movement. In addition to this feature of the INSPIRE hackathon concept, the hackathons are particularly well suited for cross-disciplinary collaboration and exchange of information. This is true also for cross regional collaboration. Some stakeholder communities will not identify or thrive in a hackathon, and this Community building concept contains descriptions or suggestions for how to create interesting meetings or activities for these communities, with a view to expand their interaction with other stakeholder groups/sub communities. This document concludes with a simple guidance for hackathons, it contains information about the main challenges and the areas of interest for the stakeholder groups so that the chosen format of engagement is made relevant to address the concerns of the community. It is through engagement one builds communities. This document will be updated to include the learnt experiences along the way.