"In our ground-breaking paper published in Nature we showed, that the atmospheric Secondary Organic Aerosol (SOA) particles formed in boreal forest can be amorphous solid in their physical phase. Our result has already re-directed the SOA related research. In the several follow-up studies, it has been shown that SOA particles generated in the laboratory chamber from different pre-cursors and in various conditions are amorphous solid.My ultimate task is to quantify the atmospheric implications of the phase state of SOA particles. Solid phase of the particles implies surface-confined chemistry and kinetic vapour uptake limitations because mass transport (diffusion) of reactants within the aerosol particle bulk becomes the rate limiting step. The diffusivity of the molecules in particle bulk depends on the viscosity of the SOA material. Hence, it would be a scientific break-through, if the kinetic limitations or the viscosity of the SOA particles could be estimated since these factors are a key to quantify the atmospheric implications of amorphous solid phase of the particles.To achieve the final goal of the research, measurement method development is needed as currently there is no method to quantify the viscosity of the SOA particles, or to study the kinetic limitations and surface-confined chemistry caused by the solid phase of nanometer sized SOA particles. The methodology that will be developed in the proposed study, aims ambitiously to quantify the essential factors affecting the atmospheric processes of the SOA particles. The developed methodology will be use in extensive measurement campaigns performed both in SOA chambers and in atmospheric measurement sites in Europe and in US maximising the global significance of the results gained in this study.The project enables two scientific breakthroughs: 1) the new methodology applicable in the field of nanoparticle research and 2) the quantified atmospheric implications of the amorphous solid phase of particles."