Big Pretty Sky Sparks

A long long time ago, in a public school not too far from where I live now, what little we know about how lightning works was explained to me.  Apparently we still don't know a lot about how it works, but it seems we're a lot better at observing it than we used to be: I never actually got to see this particular behaviour of lightning in action before today.  My brother sent me a link to this video this morning.. it's a brilliant high-speed capture of a negative stepped ladder coming down from the clouds.  One branch makes contact with the ground and creates the path for a major return stroke.  This 33 second video covers about 0.13 seconds.