Inquiry Projects are a didactic approach including elements from Project-Based Learning and Inquiry-Based Science Education. We describe the design and application of a "Research Project" with 12-years-old students on Biogeochemical Cycles, Hydrosphere and Atmosphere. In this project, students organize a Scientific Congress on Pollution and participate in it as researchers. From the results of the application, we identify key elements in developing Inquiry Projects, related to the students' self-regulation, the role of the activity context and the development of the conceptual, procedural and epistemic dimensions of the Scientific Competence.