Scientists have recently discovered thousands of microbial species living in, on, and around plant roots that help plants survive and thrive—for instance by facilitating the uptake of nutrients and water, warding off pests and diseases, and enabling plants to cope with drought, flooding, toxins, or extreme temperatures. Scientists are trying to harness these symbionts for use in agriculture. Several microbial products are already in use on the farm, and major agrochemical companies are investing heavily in research to develop others.