Up in the atmosphere, high above thunderstorm clouds or cumulonimbus, sometimes mysterious electrical discharges occur known as sprites. They appear as bursts of red light and are usually found in clusters around 50–90 km above the surface of the earth. Unlike ordinary lightning that generates a continuous electric circuit as high energy electrons move from cloud to ground, sprites are fleeting in nature, often splashing for just a few milliseconds, and because they occur so high up in the atmosphere they are difficult to observe and even more difficult to photograph. In fact, sprites were not documented until 1989, when a scientist in Minnesota accidentally caught one on videotape. These pictures were captured by Marko Korosec, from Sezana in Slovenia, while he was following storms in Vivaro, Italy.