Do you want to help build the European Research Infrastructure for Excellence in Citizen Science? The first step is happening in the upcoming ECS Collaboration Session! The RIECS-Concept project will conceptualise the European Research Infrastructure for Excellence in Citizen Science. This RI will integrate citizens’ resources, such as mobile phones and computers, with existing scientific platforms and data collections; and it will offer transversal services, improving accessibility across research communities. The RIECS-Concept project will produce two key outcomes: a conceptual design including a feasibility study, and a five-year implementation plan for the new research infrastructure. These outcomes will provide detailed insights into the diversity and maturity of the concept considering technical, operational, societal, and environmental challenges associated with establishing the permanent and shared infrastructure. This is the very first activity of many to gather inputs and community-based evidence, in collaboration with the ECS project. You will have a chance to not only learn about this important project but also to bring your own input, needs and solutions, independently of your background or scientific domains. Who can join? This Collaboration Session is aimed at the entire Citizen Science community: practitioners, students, researchers, educators, representatives of CS projects and networks, etc.