Christian Felix Klein, German mathematician, c 1880.
© Science Museum / Science & Society Picture Library
Christian Felix Klein (1849-1925) worked on geometry (including non-Euclidian geometry), function theory and elliptic modular and automorphic functions. His 'Erlanger Programm' showed how different geometries could be clasified in terms of theory. He also wrote on the history of mathematics, encouraged links between pure and applied mathematics and engineering, and promoted general mathematical education.