Theorema Egregium asserts that curvature is an invariant of the metric. Conversely, we want to know to what extent curvature determines the metric; in other words, if a diffeomorphism preserves the sectional curvature, is it an isometry? I will present R. S. Kulkarni's paper "Curvature and metric", which solves the problem for analytic metrics in dimensions greater than or equal to 4.