In King Corn, Ian Cheney and Curt Ellis, best friends from college on the east coast, move to the heartland to learn where their food comes from.  With the help of friendly neighbors, genetically modified seeds, and powerful herbicides, they plant and grow a bumper crop of America’s most-productive, most-subsidized grain on one acre of Iowa soil.  But when they try to follow their pile of corn into the food system, what they find raises troubling questions about how we eat—and how we farm.