Red sprites and blue jets are very high altitude upper atmospheric phenomena associated with thunderstorms. They have only recently been documented on camera. Red sprites are massive (as big as 20 km in size), but faint luminous flashes that appear directly above an active thunderstorm and coincide with powerful lightning strikes. Blue jets too are a high altitude optical phenomenon, but are different from sprites. They were first documented in 1994. Blue jets are optical ejections from the top of the core regions of electrically active thunderstorms, but are not directly associated with ground lightning strikes.