A genetically modified organism, or GMO, is an organism whose genetic material has been altered using biotechnology. The alteration may involve adding a gene from another species, removing a gene, or changing a gene's regulation. The first GMO was a bacterium created in 1973. The first GM crop, a tomato with delayed ripening, was approved in 1994. Since then, GM crops have spread to over 190 million hectares worldwide.

The most common GM crops are corn, soy, cotton, and canola engineered for insect resistance or herbicide tolerance. The insect-resistant traits come from Bacillus thuringiensis, a soil bacterium that produces a protein toxic to certain insects but harmless to humans. Herbicide-tolerant crops allow farmers to spray weed killers without harming the crop. Other GM crops have improved nutrition, like golden rice with beta-carotene, or resistance to drought and disease.

GMOs are controversial. Scientific consensus, supported by the World Health Organization and the National Academies of Sciences, holds that approved GM foods are safe to eat. But public concern remains, especially in Europe, where labeling is mandatory and cultivation is limited. The debate involves science, economics, and values. It is not just about the technology.

GMOs are also used in medicine. Insulin, growth hormone, and monoclonal antibodies are produced by genetically modified cells. The same technology that makes a pest-resistant plant makes a life-saving drug.