Genetic engineering is the modification of genes or creation of new genes. Its purpose can vary from creating new organisms to modifying existing organisms. Genetic engineering is commonly used in agriculture, to enhance crop yields, for drought resistance, pesticide or herbicide resistance, or to modify plants to produce particular materials for industrial use. Some animals and fish are also genetically modified in the food industry for disease resistance. It's also commonly used for research purposes, to determine gene functions and experiment with gene therapy, the use of genes to correct genetic medical conditions.