Organic compounds are emitted into the atmosphere by anthropogenic and biogenic activities, and undergo transformations through the action of oxidants, until they are completely oxidized to CO2. This oxidation is progressive and involves the formation of numerous secondary organic compounds, the most soluble and least volatile of which can be transferred to condensed phases (aerosols or cloud droplets). The work carried out at LISA aims to improve our understanding of the multiphase oxidation processes of organic compounds and to study how their evolution modifies their properties and therefore their impact on air quality and climate. To achieve this, we study processes at the molecular scale using laboratory, modeling and field approaches.