Three scientists share 2019 Nobel Prize in Physiology or Medicine

Photo taken on Oct. 7, 2019 shows the announcement of the 2019 Nobel Prize in Physiology or Medicine at the Karolinska Institute in Stockholm, Sweden, Oct. 7, 2019. The prize was awarded jointly to William G. Kaelin Jr, Peter J. Ratcliffe and Gregg L. Semenza "for their discoveries of how cells sense and adapt to oxygen availability," said the Nobel Assembly at the Karolinska Institute. (Xinhua/Zheng Huansong)