How Word & Image Work Together

In Brian Fies' talk, he mentioned how word and image worked together in his comics.  In his comics, the words and images worked together so that the viewer would need both two understand the whole.  The story would be incomplete if the viewer only saw the picture, or only saw the words.
His book, Mom's Cancer, portrays the emotions that he and his family went through while watching helplessly as their mother battled cancer.  In his book, he was able to show images that illustrated the frustration and powerlessness they felt, while adding words to supplement and increase the feeling of the pictures.
Brian Fies also talked about his second book, Whatever Happened to the World of Tomorrow?  In this book, he created two pairs of characters: Pop and Buddy, and Cap Crater and the Cosmic Kid.  Buddy is a boy that loves to read comics about the superheros Cap Crater and the Cosmic Kid.  As the book progresses, the viewer discovers that the character of Pop and Cap Crater seem to mesh together while the characters of Buddy and the Cosmic Kid also seem to mesh together.  For the comics Buddy reads, Brian Fies used images and words that hinted at previous comics that had been published around the same time that the story was set in.