Nature
The smell after rain has a name, and it comes from bacteria in the soil
That distinctive scent after a dry spell ends is called petrichor, and it comes largely from geosmin, a compound made by soil-dwelling Streptomyces bacteria. Raindrops hitting dry ground release it into the air as a fine mist. Human noses are remarkably sensitive to it, able to detect geosmin at just a few parts per trillion.