A shopper browses at a grocery store in Los Angeles. If Prop. 37 passes, about half of what you find at the grocery store would have a new label on it.
Proposition 37 could make California the first state in the country to require labels on foods made with genetically modified ingredients. It's shaping up to be one of the most contentious and expensive battles on the state's November ballot. The ballot measure raises a host of issues -- but at the heart of it there are questions about science, and how it's perceived. Reporter: Amy Standen
On one side, organic food groups have spent about $3 million in support of the labeling law. On the other, biotech firms like Monsanto and food giants like Pepsi are spending upwards of $28 million to keep GMO labels off food packages.