Serrano chiles are small hot green chiles that turns red, then yellow as they age. You can add the serrano to salsas, guacamole as well as many other Mexican dishes. Make sure to wear kitchen gloves when handing these chiles.
These chiles are easy to find in well-stocked grocery stores and local farmer's markets. The Serrano chile is hotter than the jalapeno ranking as a 7 on a relative heat scale of 1-10.