Gregory's Server
Sprites are a rare type of lightning that are very large and strike upwards.
They were only discovered in 1989 with the development of cameras because the event is too rare (although there is evidence from 1956 and maybe even earlier, but those were probably written off as demons/UFOs).
The new photo by Matthew Dominick from ISS does a great job of showing how huge sprites are with the example of the height of the Earth’s atmosphere.