The study by Bao et al. reports the direct observation and controlled creation of one-dimensional (1D) and two-dimensional (2D) periodic ripples in suspended graphene sheets using spontaneous and thermally induced longitudinal strains. The researchers manipulate the orientation, wavelength, and amplitude of the ripples by controlling boundary conditions and the thermal expansion coefficient (TEC) difference between graphene and the substrate. They measure graphene's TEC to be anomalously large and negative, approximately -7x10^-6 K^-1 at 300K. This negative TEC enhances the thermo-mechanical control of ripple properties. The study also explores the interplay between ripple mechanics and graphene's electrical properties, finding that small ripples do not significantly affect electron scattering. The findings open new avenues for strain-based engineering of graphene devices and systematic investigation of ripple-related transport effects.The study by Bao et al. reports the direct observation and controlled creation of one-dimensional (1D) and two-dimensional (2D) periodic ripples in suspended graphene sheets using spontaneous and thermally induced longitudinal strains. The researchers manipulate the orientation, wavelength, and amplitude of the ripples by controlling boundary conditions and the thermal expansion coefficient (TEC) difference between graphene and the substrate. They measure graphene's TEC to be anomalously large and negative, approximately -7x10^-6 K^-1 at 300K. This negative TEC enhances the thermo-mechanical control of ripple properties. The study also explores the interplay between ripple mechanics and graphene's electrical properties, finding that small ripples do not significantly affect electron scattering. The findings open new avenues for strain-based engineering of graphene devices and systematic investigation of ripple-related transport effects.