The Formula t-shirt by Insanely Great Tees

Like we could help ourselves from posting this. Coffee is the wellspring from which all creative thought--nay, even civilization itself!--flows.

It appears to be printed on something greyish-green or greenish-grey, depending on which pic you look at. You can see for yourself on the Insanely Great Tees site here.

Found via Shirtlog.

P.S. Just remember: decaf kills.