Have you ever sniffed the air after it rains? That smell has a name—petrichor (PEH-truh-kor).

During a storm, lighting causes molecules in the air to split and rearrange, creating a gas called ozone. Raindrops carry ozone molecules from the sky. The smell of ozone mixes with other scents from the ground.

Bacteria in the soil release compounds (mixtures of chemical elements) when it rains. The rain also stirs up compounds from plant oils.

All these scents mix to make petrichor.