Our research is focused on Analytical and Physical Chemistry of Atmospheric Aerosols and includes: (1) development and applications of novel analytical methods for comprehensive chemical characterization of aerosols, (2) chemical imaging and molecular characterization of environmental particles and interfaces, (3) laboratory and field studies of aerosol chemistry. Aerosols originate from either natural processes (e.g. sea spray, dust storms, pollen, biogenic organic particles, etc) or anthropogenic activities (e.g. combustion related emissions from industry and transportation). They can be directly emitted from a variety of sources (primary aerosols) or formed by physicochemical gas-to-particle conversion processes (secondary aerosols). Aerosolized particles are key elements in many environmental issues ranging from climate change to public health. Understanding the ways in which aerosols impact environment requires knowledge of their origin, fate, physical and chemical properties and composition. Despite their acknowledged importance, present understanding of complex multiphase chemistry of aerosols is very limited. As a result, yet their role in atmospheric environment cannot be quantitatively determined. Research projects in our group are focused on understanding the molecular chemistry of aerosols based on both field and laboratory studies. The subjects of our research projects include detailed characterization of particle composition, reaction chemistry, morphology, phase and internal structure, hygroscopic properties of particles, kinetics of gas-particle reactions, effects of particle aging and their atmospheric reactivity and transformations. Our ongoing research projects are: a) molecular-level understanding of the interactions of anthropogenic and natural emissions and their effects on the internal composition (mixing state) of individual particles and their physicochemical properties, b) understanding the origin, molecular composition and atmospheric transformations of light absorbing organic aerosols (aka ‘brown carbon’), c) understanding reaction mechanisms of atmospheric chemistry that result in increased viscosity and formation of glassy particles, understanding how these changes affect their atmospheric lifetime, heterogeneous reactions, optical and hygroscopic properties.