The PLACES - Platform for collaborative engagement on societal issues - project is a research and innovation device that will make it possible to analyse citizen science practices and develop a technical service to support them. The objective of PLACES is to propose a solution to the low societal impact of research in the Humanities and Social Sciences. PLACES is a comprehensive system for citizen science observation, which will not only make collaborative research carried out jointly by research teams and other socio-economic actors possible, but will also allow the study of their impact on society and research practices. PLACES will offer concrete technical support to citizen science while exploring diverse and joint professional practices through pilot research. Based on these collaborative researches, PLACES will study, in a comprehensive approach, the effective conditions for carrying out citizen science. The PLACES platform is based on three distinct services: community management and linking professionals (matching service); access to funding sources (international call for proposals database, international network of funders, crowdfunding tool); collaborative project management (management of user rights and profiles, connection to databases and data repositories, interoperability with other work environments, collaboration tools - including discussion and sharing - on text and multimedia data). Fully integrated into the Open Science paradigm, the system implemented by PLACES will make it possible to analyze the impact of citizen science, explore new forms of scientific communication, and reflect on the ethical and legal issues related to the publication and availability of research data according to the FAIR principles (Findable, Accessible, Interoperable, Re-usable). Finally, PLACES will promote the transfer of knowledge and know-how between researchers and other socio-economic actors.