Let's put it this way: if you are a novelist, I think you start out with a 20 word idea, and you work at it and you wind up with a 200,000 word novel. We, picture-book people, or at least I, start out with 200,000 words and I reduce it to 20.
“From the time I could play the piano, I remember trying to write tunes. They were in my head, and I would just sit down and start noodling. Next thing I knew, I had written a melody.”