Did you know? The ancient Greeks wrote in alternating directions: from left to right then right to left, without spaces between their words. An Alexandrian librarian invented punctuation in the second century B.C.E.: théseis were a series of dots that signaled the length of breath between words. An explosive string of punctuation used to signify swear words— created by Beetle Bailey cartoonist Mort Walker—is called a grawlix. Learn even more about the history, usage, and little-known facts surrounding indispensable punctuation in this "glorious celebration of those little marks that make a big difference."