Science fiction/Horror, good documentaries?

[Tradesonred]

Just saw an awesome documentary on horror films since cinema was in its infancy, called "Nightmares in red,white and blue."

Was wondering if anyone knew of some good science fiction documentaries?

I know there are some good ones with new technologies and where they might lead us, but looking more specifically for documentaries dealing with the meaning and underlying themes in specific movies and maybe one with a historical timeline of movies that were done.