Stratospheric aerosols were collected on special surfaces to determine both the physical state of the particles and the nature of included undissolved granules. Physically, each aerosol particle is composed of a somewhat volatile slurry mixture of crystalline-like material in a liquid matrix. Variations in the relative amounts of liquid at different times cause changes in particle fluidity. Although all particles contain a significant portion of the crystalline material, they are fluid in the atmosphere in the altitude range from 12 to 32 km and are physically similar at all geographic locations from 5¿N to 89¿N latitude and from 55¿W to 175¿W longitude. No evidence of frozen particles has been found even at stratospheric temperatures of -65¿C. Undissolved granules are found in only one third of the aerosol particles, and sometimes the granules are found alone outside the slurry matrix. Thus we conclude that in general, these undissolved granules are not active nucleating agents for stratospheric aerosols. Furthermore, these granules now contain mostly sulfur, sodium, and possibly lighter elements, whereas before they contained silicon and other heavy elements attributed to volcanic eruptions. We conclude that other important sources besides volcanos dominate the granular component after long quiet periods without significant volcanic activity.