Footage of red sprites during a thunderstorm. This a selection from the first footage of sprites caught from a ground camera on 7th July 1993. 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 at the Yucca Ridge Field Station, Fort Collins, Colorado, USA.