Author and illustrator Mo Willems talks about his new children book 'Are You Small?'

Award-winning author and illustrator Mo Willems' creative spark elevated him to the big time among children's book creators, but his latest work takes us into teeny-weeny territory.

Three of his books -- "Don't Let The Pigeon Drive the Bus," "Knuffle Bunny: A Cautionary Tale," and "Knuffle Bunny Too: A Case of Mistaken Identity" -- have earned Caldecott Awards, which recognize the most distinguished American picture books for children each year.

His latest book, "Are You Small?" takes readers on an adventure to introduce them to the tiniest things in the universe, from an average-size kid, to a cookie crumb, to a water molecule all the way down to a single quark.

ABC News sat down with Willems to discuss this adventure in more detail, with a special guest jumping in to help out.

ABC NEWS: Mo Willems is among the most famous, creative and prolific author-illustrators of children's books of our time. He's been awarded three Caldecott Award honors. His books, featuring beloved characters like The Pigeon, Elephant and Piggie, and Knuffle Bunny. They regularly topped the New York Times bestseller list.

If you've got kids or if you have friends who have kids, you certainly know his work and his brand new book, "Are You Small?" comes on the heels of his very successful "Are You Big?" and it's sending readers on an adventure to learn about size and scale. Mo Willems, honored to have you here. Thanks so much.

WILLEMS: It's really great to be here. Thank you Trevor.

ABC NEWS: Okay, so you have "Are You Big?" Very successful. But there was clearly still something with size left with size left to explore here. What was the idea?

WILLEMS: I think look, I right now I'm really into this idea that we are more than one thing and we are looking for our place in the world. And so the idea of how big you are, or how small you are in relationship to everything else is very, very exciting. And for me, the book is the party, but the after party is the experience you have with it.

So in this case, I'm putting in some things that you may not know or parents may not know, like what is an up quark? Then you and the parent discover that together.

ABC NEWS: And then they can learn together. Subatomic particles in the children's book.

WILLEMS: That is exactly right.

ABC NEWS: What is the balance, when you're writing a children's book, between actively trying to teach a child versus just inviting interesting moments and fun conversation?

WILLEMS: I am not trying to teach. A book is a question you don't know the answer to. And if I know the answer to that question, then I'm lecturing. And what I want to do is, I want to be a co-asker. When I ask myself, "How big am I?" "How small am I?" "What does that mean?" "What is my place in the universe?" Because that interests me.

ABC NEWS: You're kind of touching on this with that answer. I know that you've said your books are not meant to be read, they're meant to be played with. What does that mean, exactly?

WILLEMS: Well, again, it's the afterparty. So the Pigeon, for instance, was drawn so that any child can reasonably draw it. You want to play that book after you've read that book. I'm always thinking about what that next step is going to be.

ABC NEWS: Yes. And I know that you just co-founded Hidden Pigeon Company.

WILLEMS: That is correct.

ABC NEWS: So we've got the books already, but maybe expanding some further ideas.

WILLEMS: I think the Pigeon may appear randomly on television screens. When you least expect it.

"The Pigeon," a signature character in Mo Willems' books, joins the conversation.

PIGEON: What happened? What happened? I have something to say.

WILLEMS: Oh, look. Hi Pigeon! I'm just doing an interview here. It's a new story. It's very, very serious.

PIGEON: That sounds very important. I won't be that loud. Hi. Who are you?

ABC NEWS: Hi, I'm Trevor. It's nice to meet you Pigeon.

PIGEON: Trevor. Hi. I am The Pigeon.

ABC NEWS: The Pigeon. I am sorry I dropped "The."

WILLEMS:  Yes that's his first name.

PIGEON: Yes my first name is "The."

ABC NEWS: What's it been like for you to kind of evolve from just a drawing? Now we've got you here. Three dimensions.

PIGEON: Oh, it's really special. You know, I never, I actually never expected this. I started as a simple little drawing, a simple little drawing, a couple of circles and a beak.

And now, now I turn into books, and then and and then I turn into a whole puppet. And then who knows what's next? I could turn into vanilla pudding. I have no idea. The world is a crazy thing.

WILLEMS: The world is a crazy thing.

ABC NEWS: That's true. That's a great point. Mo, what's it like for you to watch your creation evolve like this?

WILLEMS: I love the idea that these characters are being played with in ways that I didn't expect. My greatest joy is when I see that a kid has made their own Pigeon book with one of their own characters. That to me is exciting. I always want to be a conduit to what that next step is, the next creative step.

ABC NEWS: The fact that we've got the puppet. Is this for larger things, beyond the books?

WILLEMS: Yes so The Pigeon is appearing, we've got a YouTube channel, and is in a series called "The Pigeon Explains" where The Pigeon explains a lot of things that The Pigeon doesn't know.

PIGEON: It's really good.

WILLEMS: We're making cartoons. I'm doing theatrical stuff. I'm doing something with the National Symphony Orchestra in September. Everything that we do, hopefully is playful for us, but will inspire kids and families to play together.

ABC NEWS: Yes. And we know that you already have it down still with the books -- Mo Willems and The Pigeon. A pleasure to meet you both. The book is "Are You Small?" Thanks so much, guys.

WILLEMS: Thank you Trevor. Do you want to take a bus home?

PIGEON: I would, can I drive it?

WILLEMS:  No I'm sorry. But you can just take the bus.

ABC NEWS: I'm sorry guys.