Wearing sunscreen is important to protect your skin from the harmful effects of UV radiation but doesn't cool people off. However, a new formula, described in Nano Letters, protects against both UV light and heat from the sun using radiative cooling. The prototype sunblock kept human skin up to 11 degrees Fahrenheit (6 degrees Celsius) cooler than bare skin, or around 6 °F (3 °C) cooler than existing sunscreens.