[Eetrab]

Never got this one until I was told either.

Week 2: What is it that the creator doesn't use, the user doesn't know he's using, and that the user is unaware it even exists?

That might as well be any concept or phenomenon that we have not discovered yet.

Case in point...
Creator: cyanobacteria
User: caveman
Thing that caveman is using but doesn't know exists: oxygen

[dlgn]

Some sort of memory-altering drug.

[MindlessInsanity]

OK Eetrab's right, it could be, but think something primitive and has been in use for a long time.

[eah]

creator: The Sun
user: plants
thing being used: sunlight

[dlgn]

I have a feeling that the answer is "a quark".

[Bu1ld0g]

You called?

[dlgn]

...forget I said anything.

[Bu1ld0g]

Too "deep" for you?

[MindlessInsanity]

Gonna give this one a few more weeks due to the lack of responses.
Hint: used by people and made by people.

[eah]

I don't care what you say. My answers are right on the money and I have another one.

creator: animals
user: plants
thing being used: carbon dioxide

If both the creator and the user are people, how is it that the creator doesn't use it? That's contradictory. And how is it that the user (people) does not know it exists when we (people) are expected to answer the riddle and therefore acknowledge its existence?

inb4 silly answer and I quit this frustrating game.