Genetically modified food (or GM food) is food produced from plants or animals whose DNA has been altered through genetic engineering. These genetically modified organisms are often called GMOs for short.

Genetic engineering is the process of manipulating an organism’s genes directly — by, for example, transplanting DNA from other organisms. It’s different from the conventional method of selectively breeding plants and animals to get desired traits. Genetically modified foods have been on the US market since 1994, ever since the introduction of ”Flavr Savr” tomatoes that had been engineered to ripen more slowly.

There’s no one type of genetically modified organism — genetic engineering is a tool that can be used for a variety of purposes. Most of the corn and soy grown in the United States has been genetically modified to be resistant to herbicides, so that it’s easier to spray fields with weed killer. Other crops have been modified to withstand pests. But genetic engineering could conceivably help create crops that can survive drought, or help produce food that’s more nutritious.

There’s a broad scientific consensus that the genetically modified foods currently on the market pose no more of a health risk than regular foods. Still, GM foods are controversial. Opponents argue that genetically modified crops can lead to things like the increased use of chemical herbicides, or cite problems with the fact that GMOs are owned and patented by large companies. That has led to debates over whether GMOs should be labeled or tightly regulated.