In his 1996 paper ''Positive curvature, macroscopic dimension, spectral gaps and higher signatures'', Gromov gave a reasonably elementary proof of Novikov's celebrated result that the rational Pontrjagin classes of the tangent bundle of a manifold are invariant under homeomorphisms. The proof uses neither surgery techniques nor results from algebraic K-theory. In this talk, I attempt to give a detailed exposition of Gromov's argument.