During the Vietnamese resistance war, Vietnamese moving down the Ho Chi Minh rail were contracting malaria in the jungle. The Chinese were asked for aid, and Tu Youyou was tasked with assembling a team to help.
One thing Tu Youyou did was consult "traditional Chinese medicine" with how to aid victims of malaria. Most of what she found did not work, but wormwood did produce results. Tu Youyou again consulted traditional Chinese medicinal texts and they said wormwood should be used with cold water. The team extracted artemisinin from the wormwood in cold water, and a new (and old) way of fighting malaria was born.