Sir Martin John Evans researched developmental biology in the United Kingdom during the twentieth and early twenty-first centuries. He was among the first to isolate and grow embryonic stem cells in the lab. Embryonic stem cells have the ability to develop into many different cell types. Using those cells, Evans and his colleagues developed methods for introducing changes to the DNA of early mouse embryos. He found that when he introduced those modified embryos into foster mothers, the genetic alterations also appeared in subsequent generations. That finding helped him produce some of the first living mice with desired genetic changes, later dubbed knockout mice. In 2007, Evans received the Nobel Prize in Physiology or Medicine along with Mario Capecchi and Oliver Smithies for their work on introducing specific gene modifications in mice using embryonic stem cells. Evans’s scientific contributions have permitted scientists to better understand the roles of different genes in both embryological development and disease.