You probably already know the story behind the famous FedEx logo and its clever use of negative space. (If you don't, read this.) But of course, it's hardly the only logo with a "hidden message."

British plastic card maker Oomph has collected 40 such logos—check them out below. Amazon, Unilever and the Tour de France are particularly cool. How many of these sneaky messages would you have spotted without the help?

Note on the BMW logo: There is some debate about that one.