Geosmin, a volatile organic compound released by some bacteria and plants, has a distinct earthy, musty odor. It is produced by Streptomyces bacteria, which thrive in moist soil. After a dry period, when the first rain falls, the water droplets "splash" the dormant bacteria cells, releasing geosmin into the air. The rain smell is commonly called petrichor, which originated from the Greek words petra, meaning "stone or rock," and ichor, meaning "fluid or blood of the gods."