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Video abstract for the article 'On the structure and topography of free-standing chemically modified graphene ' by N R Wilson, P A Pandey, R Beanland, J P Rourke, U Lupo, G Rowlands and R A Römer (N R Wilson et al 2010 New J. Phys. 12 125010). Read the full article in New Journal of Physics at http://iopscience.iop.org/1367-2630/12/12/125010/fulltext/. Part of Focus on Chemically Modified Graphene. GENERAL SCIENTIFIC SUMMARY Introduction and background. Graphene is a single-atom-thick hexagonal lattice of carbon atoms. The inter-atomic bonding might be expected to keep the sheet planar, making graphene a truly two-dimensional (2D) material, but instead ripples form in free-standing graphene. The nature of these ripples is important both fundamentally—how do 2D materials exist in a 3D world?—and practically —they have been predicted to influence the charge carrier mobilities. Graphene was first made by mechanical exfoliation from graphite; this ingenious process is laborious and not suitable for large-scale manufacture. An alternative route is chemical exfoliation, making graphene oxide (GO): graphene sheets decorated with oxygen functionalities. GO is a type of chemically modified graphene, and is the usual starting-point for further functionalization of graphene for e.g. sensors, light-harvesting and composites. Main results. We have used transmission electron microscopy, and atomic force microscopy, to study the structure of chemically modified graphene when on a surface and when free-standing. We find that, unlike graphene, suspended sheets of graphene are distorted on nanometre length scales. By comparing our experimental results with numerical simulations, we find that the mean atomic displacement from the nominal lattice position is of order 10% of the carbon--carbon bond length. Wider implications. Our results suggest a complex structure for chemically modified graphene where heterogeneous functionalisation induces local strain and distortion. Understanding this structure will help develop effective strategies for further functionalization, and advance knowledge of the electrical and mechanical properties of chemically modified graphene.