The Atmospheric Aerosol Group at the Scripps Institution of Oceanography investigates the behavior of aerosol particles in the Earth’s atmosphere under both pristine marine and polluted urban conditions. Measuring the properties of atmospheric structure and its chemical constituents is an important part of these investigations, for which our group has developed instruments that we have used in the field for airborne and shipboard observations. We have developed significant expertise in using synchrotron radiation to measure organic composition in individual organic particles with soft x-rays. Field projects are an important part of our research effort, providing evidence of the role of aerosol particles in atmospheric chemistry, meteorology, and radiation. Interpreting the results of field projects involves both analysis with numerical models of aerosol evolution and laboratory investigations.