By analyzing ancient medical texts and more than 2,000 herbal remedies, the phytochemist Tu Youyou and her team identified a plant supposedly brimming with antimalarial compounds: sweet wormwood (Artemisia annua), a member of the daisy family that looks a bit like chamomile. Upon initial testing, the plant did not perform well. But a fourth-century handbook of prescriptions provided a vital insight: To extract the plant's medicinal properties, it should be steeped in relatively cold water, rather than boiled like tea. Subsequent research identified wormwood's primary active compound, which was eventually developed into artemisinin, one of the most successful treatments for malaria in history. In 2015, Tu received the Nobel Prize in Physiology or Medicine.