He's the best-selling children's author in America today.
From his first book, "And to Think That I Saw It on Mulberry Street," which was turned down by more than 20 publishers, to his last, "Oh, the Places You'll Go!" -- 44 books in all -- Seuss was just what the doctor ordered to teach children to read at earlier ages.
You know the author, but you may not know the man behind the pseudonym, Ted Geisel, who died in 1991.
"He has been such a private person in his life that I think it has started a great, 'Who was this man?'" says Ted's widow, Audrey Geisel.
She's overseeing the "Seussentennial" -- a nationwide celebration of a century of imagination. Her husband shied from the spotlight, even when it came to the children he wrote for.
"[He] didn't want to contend with more than one or two children at one time," says Audrey. "[Seuss] found them a little surprising. He wasn't sure how to take them. He never had a child of his own."
Theodor Seuss Geisel was born in Springfield, Mass., to parents Theordor Geisel and Henrietta Seuss. His artistic genius has been cast in bronze in a memorial sculpture garden in his hometown.
"Images would stick in his mind like barnacles, and he couldn't get rid of them," says Charles Cohen, a biographer and collector of Seuss's works. "So, things around Springfield that he saw growing up would just stay with him and then show up later in his artwork.
Cohen has been on a mission to preserve "Seuss, The Whole Seuss and Nothing But the Seuss."
"He just had this very funny side ... He used to give little performances at dinner parties using silverware as characters," he says. "He kept a very wide hat selection."
It was "The Cat in the Hat," first published in 1957 and later made into an animated film, which turned Dr. Seuss into a household name. His best-selling book, "Green Eggs and Ham," was written on a $50 bet that he couldn't write an entire book using only 50 words.
"Seuss is America's most famous poet. There are very few writers who have actually changed the language," says Philip Nel, author of a new Seuss biography. "His word 'nerd,' which first appears in 'If I Ran the Zoo,' is now in dictionaries."
Nel says although Dr. Seuss's books have been translated into 20 languages, Seuss is still an American icon.
"I think Seuss speaks to particular American traits," explains Nel. "Americans like the rebel, the underdog, the outsider. Mack, who topples the stack of turtles; he's not going to take it anymore. The Cat in the Hat, who says, 'Why not fly kites in the house.' Or Sam I Am, who invites us to try green eggs and ham. I think it's a very American characteristic to celebrate the rebel."
Before writing books for children, Seuss was a political cartoonist during World War II, horrified by racism, intolerance and greed. Those messages later found their way into his books.
Before Seuss started selling ideas, he sold everything from beer to ball bearings as an advertising man.
"He did several different commercials for the Ford Motor Car Company in 1949 to 1950," says Cohen.
But he is most famous for a campaign for Flit bug spray. "Quick, Henry, the flit," became a national catch phrase. It was the "Where's the beef" of its day.
Seuss's adult sense of humor sometimes surprised his publishers.
"There's a story that one of his editors tells about Dr. Seuss's ABC and for the letter X," says Nel. "Dr. Seuss has drawn a large-breasted woman and the following verse, 'Big X, Little X, XXX. Someday kiddies you will learn about sex.' That's not actually in the book. That was just there to make sure the editors were paying attention. And they were."
As a writer, Dr. Seuss didn't exactly just pull words out of a hat.
"Seuss was a master of the art of revision -- write, rewrite, reject, re-reject and polish incessantly," says Nel.
"The Cat in the Hat"'s line, "He came down with a bump from up there on the ball" began as "He fell off the ball."
Seuss's legacy is the poetry, the politics and the art. It is the idea that reading should be fun and that children's books can make you think.