The idea of writing a book for kids that manages to cover colors, counting, days of the week, healthy eating and the process of metamorphosis sounds impossible. All the more reason to admire what might well be the world's most perfect picture book. As Carle himself once said of his work, it's a book of hope for any child who feels small and helpless and wonders if they'll ever grow up. In other words, it's for the future butterflies of the world. Good thing Carle's editor convinced him to make the book about a caterpillar instead of Carle's original Willie Worm. Penguin. Ages 6 months to 3 years.