The physical and chemical properties of aerosol particles and trace gases effect the air quality and climate. It’s important to understand how atmospheric aerosols form and the role they play in the Earth's climate through their interactions with clouds. Besides understanding the mechanisms of cluster and new particle formation, it is also crucial to understand the chemical reactions leading to production of the cluster/particle precursor vapours. In addition, it is important to investigate the sources and processes modifying atmospheric aerosol populations, interaction between aerosols, clouds and radiation, and the associated feedback mechanisms. One of our research topics is to investigate the formation and growth of secondary organic aerosols inside the planetary boundary layer.