Through genetic engineering, scientists can pull off such outrageous-sounding feats as crossing a tomato with a flounder. In fact, more than half of the foods on grocery store shelves now—even infant formula—have been genetically modified in some way. But do we really know yet whether they are safe for humans and the environment? Bill hears the various sides of this controversial issue by talking to traditional wheat breeders, organic agriculture researchers, and corporate genetic engineers.