Ohm taught him at school. Studying in Paris, he came into contact with Biot, Legendre, Laplace and Hachette, while meeting Fourier and Poisson stimulated his interest in mathematical physics. Fourier, Humboldt (who encouraged him to return to Germany) and Gauss (whom he eventually succeeded) all helped him in his career. He was Jacobi’s great friend, and Babbage’s guide in Berlin. Riemann (who revered him, and became his colleague) was among his students, who often spent afternoons at ‘Kaffeehaus Dirichlet’. He married the Mendelssohns’ sister and adopted Fanny’s son; Joachim and Scumann played at their parties.