the Institut des Hautes Etudes Scientifiques, which I frequented throughout the year 1965, profoundly changed my mathematical universe." After this event, singularity theory became one of the major interests of Arnold and his students. Among his most famous results in this area is his classification of simple singularities, contained in his paper "Normal forms of functions near degenerate critical points, the Weyl groups of Ak,Dk,Ek and Lagrangian singularities". Fluid dynamics In 1966, Arnold published "", in which he presented a common geometric interpretation for both the Euler's equations for rotating rigid bodies and the Euler's equations of fluid dynamics, this effectively linked topics previously thought to be unrelated, and enabled mathematical solutions to many questions related to fluid flows and their turbulence. Real algebraic geometry In the year 1971, Arnold published "On the arrangement of ovals of real plane algebraic curves, involutions of four-dimensional smooth manifolds, and the arithmetic of integral quadratic forms", which gave new life to real algebraic geometry. In it, he made major advances in the direction of a solution to Gudkov's conjecture, by finding a connection between it and four-dimensional topology. The conjecture was to be later fully solved by V. A. Rokhlin building on Arnold's work. Symplectic geometry The Arnold conjecture, linking the number of fixed points of Hamiltonian symplectomorphisms and the topology of the subjacent manifolds, was the motivating source of many of the pioneer studies in symplectic topology. Topology According to Victor Vassiliev, Arnold "worked comparatively little on topology for topology's sake." And he was rather motivated by problems on other areas of mathematics where topology could be of use. His contributions include the invention of a topological form of the Abel–Ruffini theorem and the initial development of some of the consequent ideas, a work which resulted in the creation of the field of topological Galois theory in the 1960s. Theory of plane curves According to Marcel Berger, Arnold revolutionized plane curves theory. Among his contributions are the Arnold invariants of plane curves. Other Arnold conjectured the existence of the gömböc. Honours and awards Lenin Prize (1965, with Andrey Kolmogorov), "for work on celestial mechanics." Crafoord Prize (1982, with Louis Nirenberg), "for contributions to the theory of non-linear differential equations." Elected member of the United States National Academy of Sciences in 1983). Foreign Honorary Member of the American Academy of Arts and Sciences (1987) Elected a Foreign Member of the Royal Society (ForMemRS)