The article summarises eight years of the Samen Meten initiative by the Dutch National Institute for Public Health and the Environment (RIVM), showing how citizen-led air quality monitoring adds value to traditional systems. It highlights how low-cost sensors enable more frequent and spatially detailed measurements, providing insights into local pollution patterns when combined with official data. The initiative also strengthens collaboration between citizens, scientists, and government (dialogue), while offering tools, guidance, and a shared data infrastructure that supports data collection, visualisation, and analysis. Overall, Samen Meten demonstrates how citizen science can enhance environmental monitoring, improve research quality, and build trust, forming a scalable infrastructure for future monitoring of air, water, and soil.