Bernhard Riemann

Georg Friedrich Bernhard Riemann (Breselenz, 17 September 1826 – Selasca, 20 July 1866) was a German mathematician who made important contributions to differential geometry, the theory of functions, and number theory.

Biography
Riemann was born into a Lutheran pastor's family in the Kingdom of Hanover. Already as a schoolboy he read advanced mathematical books, including Adrien-Marie Legendre's Number Theory (1830). He studied mathematics at the University of Göttingen in 1846–47 and at the University of Berlin in 1847–49. In 1849 he returned to Göttingen where he started his PhD work on function theory. In 1851 he received his degree and became assistant to the mathematical physicist Wilhelm Eduard Weber and finished his "Habilitation" (advanced Doctor's degree) in 1854. In 1857 he received an appointment as "Professor Extraordinarius" (kind of associate professorship, financially supported mainly by students following the lectures of the professor) and  at the age of thirty three he became a full professor in Göttingen. His predecessor on the chair of Carl Friedrich Gauss was Peter Gustav Dirichlet, who had died. In 1862 Riemann married Elise Koch and had a daughter named Ida, who was born in Pisa (1863). Shortly after the marriage he fell seriously ill with tuberculosis. Repeated trips to Italy failed to stem the progress of the disease, and he died thirty nine years old in Italy in Selasca (now a hamlet of Verbania on Lake Maggiore).

Works
Notwithstanding his short life, Riemann is one of history's prominent mathematicical geniuses with great influence lasting to the present day. His habilitation's work on differential geometry was carried on by the Italian school of mathematicians, such as Beltrami,  Ricci, Bianchi, and Levi-Civita, culminating into the branch of mathematics that physicists call tensor analysis. This is the part of mathematics that formed the toolbox of Albert Einstein when he formulated the theory General Relativity. So, one could say that Riemann's habilitation thesis laid the foundation for the theory of general relativity.