The article discusses the structure of suspended graphene sheets, which are individual, atomically thin layers of graphene that have been isolated and suspended on a microfabricated scaffold in vacuum or air. Despite being strictly two-dimensional (2D), these graphene sheets exhibit long-range crystalline order but are not perfectly flat, showing intrinsic microscopic roughening. Transmission electron microscopy (TEM) studies reveal that the surface normal of the graphene sheets varies by several degrees, and out-of-plane deformations can reach 1 nm. The authors use TEM to analyze the diffraction patterns of these graphene sheets, which show broadening of diffraction peaks with increasing tilt angle, indicating the presence of corrugations. These corrugations are found to be static and are consistent with the high mobility of charge carriers in graphene. The observed corrugations provide a possible explanation for the stability of 2D crystals, suggesting that the interaction between bending and stretching phonons can stabilize atomically thin membranes through their deformation in the third dimension. The study highlights the unique properties of suspended graphene sheets and their potential applications in various fields, such as high-resolution electron microscopy and nanomechanical devices.The article discusses the structure of suspended graphene sheets, which are individual, atomically thin layers of graphene that have been isolated and suspended on a microfabricated scaffold in vacuum or air. Despite being strictly two-dimensional (2D), these graphene sheets exhibit long-range crystalline order but are not perfectly flat, showing intrinsic microscopic roughening. Transmission electron microscopy (TEM) studies reveal that the surface normal of the graphene sheets varies by several degrees, and out-of-plane deformations can reach 1 nm. The authors use TEM to analyze the diffraction patterns of these graphene sheets, which show broadening of diffraction peaks with increasing tilt angle, indicating the presence of corrugations. These corrugations are found to be static and are consistent with the high mobility of charge carriers in graphene. The observed corrugations provide a possible explanation for the stability of 2D crystals, suggesting that the interaction between bending and stretching phonons can stabilize atomically thin membranes through their deformation in the third dimension. The study highlights the unique properties of suspended graphene sheets and their potential applications in various fields, such as high-resolution electron microscopy and nanomechanical devices.