Carbon.
The Big Bang Theory Season 12, Episode 23
I don't know. How do CARBON atoms
form a benzene ring?
The Big Bang Theory Season 2, Episode 13
Did you give any consideration
to CARBON nanotubes?
The Big Bang Theory Season 1, Episode 12
refine it into CARBON dust,
The Big Bang Theory Season 7, Episode 7
Needed bigger CARBON atoms.
The Big Bang Theory Season 3, Episode 14