Bernard Riemann

Possibly the greatest Mathematician, along with Euler and Gauss (his teacher). Among his achievements, one should mention:

• Riemannian geometry: generalization of (Euclid's) geometry to all shapes in any number of dimensions.
• Riemann hypothesis: the Riemann $\zeta$ function has its zeros only at the negative even integers and complex numbers with real part 1/2.
• Cauchy–Riemann equations: conditions for a complex function to be differentiable.
• Riemann surface: support of analytic function in complex calculus.
• Riemann integrals: the rigorous version of a pillar of calculus, updated only with Lebesgue and measure theory.

He studied philology and Christian theology, even thinking of becoming a pastor and pursuing a degree in theology, but Gauss persuaded him to study mathematics instead. Riemann remained a dedicated Christian who saw his life's work as a way to serve God. His tombstone in Biganzolo (Italy where he took refuge ) reads:

For those who love God, all things must work together for the best.

—Romans 8:28