Teem, an app focused on increasing the participation and sustainability of commons-based peer production communities (e.g. Wikipedia, free software, Arduino), although it may be applied to other open online communities (networks, open organizations) or even social movements (social centers, collectives). After doing intensive social research and prototype testing, we are aware of the main needs of the different roles within a community (following the classical 1-9-90 rule: core, occasional collaborators and users), and the tools they typically lack (related to management and internal organization, listing the subprojects available and the needs of each). The app is grounded on these findings to reduce the frustrations of all participants and increase participation (90s=>9, 9s=>1)... while providing a kind-of project management tool for communities (but informal/liquid/open to fit the context) together with a work-space with collaborative edition (like a google-doc) and a group chat (like a whatsapp/telegram group).