Hans Spemann (June 27, 1869 - September 9, 1941) was a German embryologist. In 1914, He as appointed Associate Director of the Kaiser Wilhelm Institute of Biology and began the experiments that would make him famous, grafting a field of cells from one embryo onto another. In 1928 he was the first to perform somatic cell nuclear transfer using amphibian embryos. He was awarded the Nobel Prize in 1935 for his discovery of the effect now known as embryonic induction, an influence, exercised by various parts of the embryo, that directs the development of groups of cells into particular tissues and organs. His theory of embryonic induction is described in his book Embryonic Development and Induction (1938). He died of heart failure in 1941 at the age of 72,