Recombinant DNA technology (genetic engineering) alters the genetic material of organisms. In doing so, horizontal gene transfer is used to manipulate the genetic information of microorganisms, plants and animals, whereby they acquire some desirable properties that they did not possess until then. This process has resulted in several, mainly plant organisms, which are used in human and animal nutrition and which are called genetically modified (GM) foods. Nowadays, genetically modified cultivars of soybean, oilseed rape, potatoes, corn and rice are the most present on the world market. They have several advantages over conventional cultivars, including resistance to insects, diseases and herbicides, improved nutritional value, growth in adverse climatic conditions, faster growth than conventionally grown plants, lower pesticide consumption and, in general, lower production costs. The World Health Organization and many prestigious scientists agree that GM food approved for the market is not more harmful to human health than conventionally grown food and that in many cases GM food is safer than traditionally grown food because it is subject to much greater control. Nevertheless, GM food is still a very current topic around which there are divided views, mostly on the issue of GM food safety for human health, its impact on the environment and the possible socio-economic consequences of its cultivation.