Petrichor

Petrichor is the pleasant, earthy scent that often accompanies the first rain after a long period of dry weather. It's the smell that permeates the air when raindrops fall on dry soil. The term comes from the Greek words "petra," meaning "stone," and "ichor," which is the fluid that flows in the veins of the gods in Greek mythology.

The scent itself arises from a combination of factors. One of the main contributors is an oil produced by certain plants during dry periods, which is absorbed by soil and rocks. When it rains, compounds from the oil are released into the air. Another contributor is the compound geosmin, a metabolic by-product of certain bacteria in the soil, which also gets released into the air when it rains. Humans are particularly sensitive to geosmin and can detect it at very low levels, which is why the smell of petrichor is so noticeable and distinct.