In mid-October 2006, I drove from Indianapolis to Bloomington to tour Indiana University, a prospective college. Having grown up in Connecticut, the Midwest looked like another planet to me: mile after mile of flat, verdant cropland. As I gazed at the sea of gold-tipped cornstalks, little did I know that 40 percent of Indiana corn that year was genetically modified. Six years later, that percentage more than doubled to 84 percent.

In recent years, people worldwide have become more aware of the prevalence of genetically modified organisms, or GMOs. Nearly 2 million people participated in a global non-GMO “March Against Monsanto” in May of this year. More than 20 states, including Washington, Oregon, and Vermont, now have GMO-labeling legislation in the works. And in a game changing move, Whole Foods Market announced in March that by 2018 all items sold in its stores must include GMO labeling. “We are putting a stake in the ground on GMO labeling to support the consumers’ right to know,” said Whole Foods co-CEO Walter Robb.

But for many people, GMOs are still a mystery. What are they? How do they impact our health and environment? And what’s being done to label them? Here’s a quick overview of GMOs from seed to plate.