By some estimates, 80 percent of all processed foods -- cereals, baby formula, canned soups and more -- contain at least one GMO, or Genetically Modified Organism. But whether GMOs are safe and whether they should be listed on the label has led to a very big food fight. Our Cover Story is from Barry Petersen:

Delan Perry's papaya farm on the Big Island of Hawaii may be a bit off the beaten path. But it's smack in the middle of a worldwide debate about one of life's essentials: the very food we eat.

His papayas, like almost all those now grown on the Big Island, are GMOs -- genetically-modified organisms.

"I'm sure their first question is, 'Is it safe?'" asked Petersen.

"We say, 'Of course!'" laughed Perry. "Been eating it, my kids have been eating it for 20 years now."

Twenty years ago, the Big Island's papaya industry had been thriving; growers were shipping 60 million pounds of papayas a year. But then insects began spreading a devastating virus called ringspot to nearly every papaya tree on the island. In about three years, the trees were dead. Fields were barren. The industry was literally wiped out.

But a Hawaiian-born plant pathologist, Dennis Gonsalves (then a professor at Cornell University in Ithaca, New York), came to the rescue.

"We had a technology that could help develop a virus-resistant papaya," he said.

Gonsalves and a team of scientists pulled off a remarkable feat of genetic engineering: they took a DNA strand from the destructive papaya virus and inserted it into the DNA of a papaya seed. Just as with a vaccine for a human, the papayas became immune to ringspot.

One of the final field tests was on Delan Perry's farm in 1997. Photos show the dead and diseased trees surrounding the healthy, genetically-engineered trees.

"It grew beautiful, absolutely beautiful," Gonsalves said. "And even to this day, there has been no breakdown of resistance."

Today, American farmers grow about 10 different GMO crops, including more than 92 percent of all corn and soy. Most are engineered to ward off insects, or to resist weed-killing herbicides (or both). That means farmers can dramatically reduce insecticide use. And when they spray for weeds, the herbicide won't kill their crops.

And most of us eat GMOs every day, in processed foods like soda, cereal, chips and cheese. in November, salmon joined the list; it's genetically engineered to grow faster.

And there are more foods in the pipeline, among them a peanut without the toxin that triggers deadly allergies; and cassavas and bananas (the main source of food for hundreds of millions of Africans) that would become immune to diseases now decimating those crops.

So given all that, why are so many people so opposed to GMOs?

"As a mother and a scientist who's been looking at these issues for some decades, I am increasingly concerned at the ways in which corporations have gained more and more control and influence over our food system," said Marcia Ishii-Eiteman, a senior scientist at the Pesticide Action Network.

Marcia Ishii-Eiteman, of the Pesticide Action Network, with correspondent Barry Petersen. CBS News

"Genetically-engineered seeds are responsible for an enormous increase in the use of pesticides, primarily herbicides -- weed killers," she said. "People have a healthy skepticism to corporations telling us that their products are perfectly safe. We've seen that with DDT and tobacco, for example."

A lot of the opposition to GMOs (dubbed "Franken-Food") is directed at the world's largest seed company, Monsanto. Ishii-Eiteman says she is troubled that when farmers buy herbicide-resistant GMO seeds from Monsanto, they are locked into using large quantities of Monsanto-produced herbicide as well.

And there's something else: Farmers who buy Monsanto's patented GMO seeds must sign an agreement promising that they will use them for only one harvest, or be sued.

"Farmers have done this since the beginning of farming -- they raise their crops, and they save their seeds and they plant them the next year," said Petersen. "So why push farmers not to plant seeds that are patented from Monsanto from this year to next year?"

"We spend a billion and a half dollars a year on research and development," said Hugh Grant, the CEO of Monsanto. "And there needs to be some way of seeing a return on that."

Grant says farmers who want to take their business elsewhere they have plenty of options.

"The grower has very little loyalty," Grant said. "They're looking for the best possible seed that produces the best possible crop."

But those crops are getting harder to sell, as consumers say they don't want GMOs in their food.