Genetically modified organisms (GMOs) are organisms whose genetic material has been altered using genetic engineering techniques. This allows genes from different species to be combined into new sets of genes. Potential advantages of GMOs include preventing disease in plants and animals that are genetically prone and treating infectious diseases. Genes can also be manipulated to help reduce threats like global warming. However, some scientists are concerned that introducing modified genes could irreversibly impact nature's complex relationships in unknown ways. Genetic engineering also raises moral issues about whether humans should manipulate nature.