Under some conditions, these particles may grow larger and form solid pieces of ice,or hail.

VOA: special.2010.01.05

These extremely small particles are believed to be linked to comets.

VOA: special.2009.01.20

These crystals grow from water particles in cold clouds.

VOA: special.2010.01.05

These can be sulfate,nitrate, ammonia,sodium chloride and if these are small particles they can be dangerous because if they are inhaled they can reach the lungs."

VOA: standard.2010.04.16