Genetically modified foods (GM foods, or biotech foods) are foods produced from genetically modified organisms (GMOs), specifically, genetically modified crops. GMOs have had specific changes introduced into their DNA by genetic engineering techniques. These techniques are much more precise than mutagenesis (mutation breeding) where an organism is exposed to radiation or chemicals to create a non-specific but stable change. Other techniques by which humans modify food organisms include selective breeding and somaclonal variation. Commercial sale of genetically modified foods began in 1994, when Calgene first marketed its Flavr Savr delayed ripening tomato. Typically, genetically modified foods are transgenic plant products: soybean, corn, canola, and cotton seed oil. These may have been engineered for faster growth, resistance to pathogens, production of extra nutrients, or any other beneficial purpose. GM livestock have also been experimentally developed, although as of July 2010 none are currently on the market. While there is broad scientific consensus that food on the market derived from GM crops pose no greater risk to human health than conventional food, critics have objected to GM foods on several grounds, including safety issues,ecological concerns, and economic concerns raised by the fact GM plants (and potentially animals) that are food sources are subject to intellectual property law.