Scaling behavior of ripple dynamics in graphene. We are studying the dynamical behavior and intrinsic stability of graphene sheets as a function of sample size and boundary conditions. The recent discovery of graphene has sparked much interest; however, a predictive understanding of the physical structure of graphene, a single layer of carbon atoms densely packed in a honeycomb crystal lattice, remained unclear. Both theory and experiments have shown that graphene has a tendency to be crumpled, since graphene appears to be a truly 2D material, exhibiting such a high crystal quality. Our molecular dynamics simulations showed that freely suspended graphene sheets in a 3D space do not remain perfectly flat: graphene sheets exhibit intrinsic microscopic roughening cause by ripples. A typical snapshot of a graphene sheet consisting of 1.0 million atoms relaxed at room temperature is shown above.