There’s little argument over what genetic engineering is: Scientists remove a gene from one organism and transfer that gene to a different organism. Unlike traditional methods, where farmers might breed plants from the same species to make a stronger plant, GE technology makes it possible to transfer any gene from any organism into a foreign one.

For example, Bt corn, introduced in 1996, contains a gene from soil bacteria that’s toxic to insects. Scientists first isolate the desired bacterium’s DNA. “They then use a ‘gene gun’ to shoot [the bacteria] genes into a petri dish full of corn embryos,” explains Gregory Jaffe, director of biotechnology projects at the Center for Science in the Public Interest. “They hope a bit of DNA randomly gets through the corn cell membrane. If it does, scientists take that embryo and grow a plant from it.” The resulting plant expresses the gene—in Bt’s case, an insecticide—in every one of its cells, enabling the corn itself to kill bugs. This scenario would never occur in nature, but as of 2012, Bt corn takes up 67 percent of all American corn acreage.