XPS and other surface sensitive methods are being increasingly used to extract quantitative information about organic and inorganic coatings and contamination on nanoparticles. The extraction of coating thickness requires information about particle diameter from other measurements, such as electron microscopy, combined with a model that includes the physical processes associated with XPS. Advantages of using XPS include the sensitivity to very thin coatings (or surface contamination) and the ability to extract important information about organic layers. Single particle information from electron microsocpy combined with XPS sensitivity in determining composition make a powerful combination for nanoparticle anlaysis.