A (very) Brief History of Charles Ehresmann

Charles Ehresmann (19 April 1905 – 22 September 1979) was a German-born French mathematician who worked in differential topology and category theory. He was an early member of the Bourbaki group and is known for his work on the differential geometry of smooth fiber bundles, notably the Ehresmann connection, the concept of jet bundles, and his seminar on category theory.

Ehresmann first investigated the topology and homology of manifolds associated with classical Lie groups, such as Grassmann manifolds and other homogeneous spaces. 

He developed the concept of fiber bundle, building on work by Herbert Seifert and Hassler Whitney. Norman Steenrod was working in the same direction in the USA, but Ehresmann was particularly interested in differentiable (smooth) fiber bundles, and in differential-geometric aspects of these.

He was a pioneer of differential topology. By 1957, having become a leading proponent of categorical methods, he founded the mathematical journal Cahiers de Topologie et Géométrie Différentielle Catégoriques.

His publications include the books 1965 Catégories et structures (Dunod, Paris, 1965) and Algèbre (1969). His collected works, edited by his wife, appeared in seven volumes in 1980–1983 (four volumes published by Imprimerie Evrard, Amiens, and the rest in the journal Cahiers de Topologie et Géométrie Différentielle Catégoriques which he had founded).