Ants, hail, pollen.. even salmonella.
Ants
(Picture: US Geological Survey) Mites
(Picture: US Department of Agriculture) Soft hail
(Picture: File) Bacteria
(Picture: Geralt) Sand
(Picture: Klaber) Orchard bee
(Picture: US Geological Survey) MRSA
(Picture: National Institutes of Health) Salmonella
(Picture: File) Snowflakes
(Picture: Michael) Pollen
(Picture: Dartmouth College) 
