Ennio De Giorgi (8 February 1928 – 25 October 1996), a member of the House of Giorgi, was an Italian mathematician who worked on partial differential equations and the foundations of mathematics. Mathematical work De Giorgi's first work was in geometric measure theory, on the topic of the sets of finite perimeters which he called in 1958 as Caccioppoli sets, after his mentor and friend. His definition applied some important analytic tools and the De Giorgi's theorem for the sets established a new tool for set theory as well as his own works. This achievement not only brought Ennio immediate recognition but displayed his ability to attack problems using completely new and effective methods which, though conceived before, can be used with greater precision as shown in his research works. He solved Bernstein's problem about minimal surfaces for 8 dimensions in 1969 with Enrico Bombieri and Enrico Giusti, for which Bombieri won the Fields Medal in 1974. His earliest work was on the aim to develop a regularity theory for minimal hypersurfaces, changing how we view the advanced theory of minimal surfaces and calculus of variations forever. The proof required De Giorgi to develop his own version of geometric measure theory along with a related key compactness theorem. With these results, he was able to conclude that a minimal hypersurface is analytic outside a closed subset of codimension at least two. He also established regularity theory for all minimal surfaces in a similar manner. He solved 19th Hilbert problem on the regularity of solutions of elliptic partial differential equations. Before his results, mathematicians were not able to venture beyond second order nonlinear elliptic equations in two variables. In a major breakthrough, De Giorgi proved that solutions of uniformly elliptic second order equations of divergence form, with only measurable coefficients, were Hölder continuous. His proof was proved in 1956/57 in parallel with John Nash's, who was also working on and solved Hilbert's problem. His results were the first to be published, and it was anticipated that either mathematician would win the 1958 Fields Medal, but it was not to be. Nevertheless, de Giorgi's work opened up the field of nonlinear elliptic partial differential equations in higher dimensions which paved a new period for all of mathematical analysis. Almost all of his work relates to partial differential equations, minimal surfaces and calculus of variations; these notify the early triumphs of the then-unestablished