Our work encompasses the analysis of ambient air pollutants using reference- or research-grade instruments and low-cost sensors. We go beyond PM mass concentrations to investigate aerosol composition with state-of-the-art filter-based laboratory analysis and in-situ instrumentation. Our expertise in the proper, science-guided use of these techniques is obtained by conducting field campaigns, source apportionment studies, and systematic evaluations of low-cost sensors, as well as literature reviews. We share this knowledge with the wider community through capacity-building workshops, data portals, and scientific publications. Our data are used to inform policyand support model development.