You may appreciate this memorable portrait as much as the next fellow, but it’s still fair to wonder: “Did it really change history?” Rest assured, we think it did. While Einstein certainly changed history with his contributions to nuclear physics and quantum mechanics, this photo changed the way history looked at Einstein. By humanizing a man known chiefly for his brilliance, this image is the reason Einstein’s name has become synonymous not only with “genius,” but also with “wacky genius.”

So why the history-making tongue? It seems Professor Einstein, hoping to enjoy his 72nd birthday in peace, was stuck on the Princeton campus enduring incessant hounding by the press. Upon being prodded to smile for the camera for what seemed like the millionth time, he gave photographer Arthur Sasse a good look at his uvula instead. This being no ordinary tongue, the resulting photo became an instant classic, thus ensuring that the distinguished Nobel Prize-winner would be remembered as much for his personality as for his brain.