The little gray cells

The little gray cells
 

The fictional Belgian private detective Hercule Poirot often says things like "The little gray cells, they are talking to me," and "What might the little gray cells be telling me?," etc. to mean he's figuring out the solution to a crime while at the same time understating his own very considerable brain-power. How would such an idea be expressed in Spanish, las pequeñas células cefálicas or something less literal?

More literal, "gray cells" = "células grises" :)