Mathematics, physics and philosophy in Riemann's work and beyond

This is the introduction I wrote for the multi-authored book "From Riemann to differential geometry and relativity", edited by L. Ji, A. Papadopoulos and S. Yamada (Berlin, Springer verlag, 2017). The book consists of twenty chapters, written by various authors. This introduction, besides giving the information on the content of the book, is a quick review of the topics on which Riemann worked and of the impact of this work on mathematics (topology, complex geometry, algebraic geometry, integration, trigonometric series, Riemannian geometry, etc.), philosophy and physics.