For centuries, humans have searched for crop plants that can survive and produce in spite of insect pests. Knowingly or unknowingly, ancient farmers selected for pest resistance genes in their crops, sometimes by actions as simple as collecting seed from only the highest-yielding plants in their fields. With the advent of genetic engineering, genes for insect resistance now can be moved into plants more quickly and deliberately. Bt technology is only one example of ways genetic engineering may be used to develop insect resistant crops now and in the future