Atmospheric particulates—tiny particles in the air—represent an exciting new research area for mineralogists and geochemists. Emitted directly into or formed within the atmosphere, these particles are generated by both natural processes and human activity. Although derived mostly from sources that are spatially and temporally confined, the particles are ubiquitous globally due to atmospheric circulation. Depending on their physical and chemical properties, these small particles have local- to planetary-scale environmental impacts, influencing the radiative properties of the atmosphere and the cryosphere, the nucleation of both warm and ice clouds, and the nutrient contents of oceans and soils. Because airborne particles can affect human health and transportation, mainly aviation, they have become a focus of government attention and regulation.