Formation of aerosol nanoparticles from gaseous precursors is among the biggest sources of cloud condensation nuclei thus impacting global climate and air pollution. In order to gain insight on molecular level of aerosol nanoparticle formation the group of Paul Winkler uses self-made instruments quantifying particle size evolution and concentration of particles in the sub-10 nm size range. Part of the experiments are conducted in collaboration with the CLOUD experiment at CERN, Switzerland. Recent developments address formation and characterization of nanoparticles originating from plastics.