Best known for the children's classic Where the Wild Things Are, Sendak was also an illustrator and designed sets for the ballet and opera.
With the publication of Where the Wild Things Are in 1963, Sendak felt that he had ended his apprenticeship. His childhood experiences, years of illustrations for other authors' books, and psychoanalysis came together in the fantasies of Max, the boy in the story who is sent to bed without his supper, and the monsters he encounters in the world of the wild things. The story is rooted in the very real fears that children have of being left alone or not cared for by their parents. Many critics and child psychologists, such as Bruno Bettelheim, felt that the book was too scary for sensitive children. Sendak was vindicated when the book won the Caldecott Medal in 1964. In his acceptance speech, he said, "from their earliest years children live on familiar terms with disrupting emotions, fear and anxiety are an intrinsic part of their everyday lives, they continually cope with frustrations as best they can. And it is through fantasy that children achieve catharsis. It is the best means they have for taming Wild Things."