Sophus Lie (1842–1899) was born in Nordfjordeid, Norway. He revolutionized the theory of differential equations through his theory of continuous transformation groups, the Lie groups named after him. By studying the symmetries of the equations, his theory unifies all analytic techniques for solving differential equations in a single framework. Lie theory forms today’s foundation for the cornerstones of theoretical physics such as general relativity and the standard model of particle physics. It is worth mentioning that his analytic solution techniques were too advanced for practical computations in the 19th century, but the advent of computers turned Lie theory into a powerful computational tool in countless application areas. Current research in algebra, geometry, and computational differential equations is brought together by Lie theory as a common theme, yielding advancement and unification of central areas of pure and computational mathematics.