Susan Cooper's poem "The Shortest Day," celebrating the winter solstice, is also a children's book illustrated by Carson Ellis. They collaborated by mail.

For "The Shortest Day," Susan Cooper collaborated with Carson Ellis, the illustrator, by mail. COOPER: I said in a letter to Carson that there is no story in this poem.

For NPR's series "Picture This," illustrator Carson Ellis talks about working with author Susan Cooper to make Cooper's poem "Shortest Day" into a children's book. (This story first aired on ...