I'm trying to do some research on dilithium but there seems to be no concise history. I would like to know very first episode it was mentioned in. I think it was the The Alternative Factor but am not sure. Though I am pretty sure it was referred to as merely lithium in the earlier episodes Where No Man Has Gone Before and Mudd's Women. Also seeking opinions as to what would be the "key" or "best" episode to watch from each Star Trek series that dilithium played an important role? I'm very familiar with Star Trek IV (don't know how many times I've seen it) but no television episode of, say, TNG jumps out in my mind where dilithium was an important plot element. Or DS9, for that matter. Not evens sure if the station used dilithium... any help would be appreciated!