Footage of a thunderstorm, with portions slowed down to show red sprites. Red sprites are faint high-altitude electric discharges. They are triggered by positive cloud-to-ground lightning in the storm below. They can rise to heights of 97 kilometres, reaching the bottom of the ionosphere and the edge of space. They last for a few thousandths of a second, and are only visible under the right conditions. Their existence was only confirmed in 1989 and their formation is still not fully understood. Filmed in South Dakota, USA.