Volcanoes can spew lava, ash and smoke when they erupt. But even when they aren't erupting, gases can leak from their vents and form tiny particles in the atmosphere known as volcanic aerosols. Although smaller than a human hair, these particles can have a large effect on the properties of nearby clouds. A new study using NASA and European Space Agency satellite data has shown that volcanic aerosols can decrease the size of water droplets that make up clouds. The result may not seem significant, but clouds composed of smaller droplets tend to be brighter and reflect more sunlight back into space. This can affect weather patterns, such as altering winds and where rain falls. Watch the video to learn more.