I always thought it was the little grey cells of the brain.

"Look, all anyone needs is one eye and a few gray cells."

A dark gray cell indicates the character does not appear in the film.

And the good heart, it is in the end worth all the little grey cells.

All that 'little gray cells' stuff he goes on about.

I have no idea what these particular grey cells are for.

"This makes the gray cells stand at attention," she had announced after the second cup.

Yes, here and now, we are going to exercise our little gray cells.

That the basic stuff my little gray cells are asking for.

There was a reason he hadn't spoken and it had nothing to do with gray cells working.