This paper presents a novel method for optical nano-imaging of gate-tuneable graphene plasmons using near-field scattering microscopy with infrared excitation. The authors demonstrate the ability to launch and detect propagating optical plasmons in tapered graphene nanostructures, providing real-space images of plasmonic field profiles. They find that the extracted plasmon wavelength is significantly shorter than the illumination wavelength, over 40 times smaller. This strong optical field confinement allows the graphene nanostructure to act as a tunable resonant plasmonic cavity with an extremely small mode volume. The cavity resonance is controlled in-situ by gating the graphene, enabling complete switching on and off of the plasmon modes. This work paves the way for the development of graphene-based optical transistors and other nano-optoelectronic devices, offering unprecedented active subwavelength-scale optics and enhanced light-matter interactions for quantum devices and biosensing applications.This paper presents a novel method for optical nano-imaging of gate-tuneable graphene plasmons using near-field scattering microscopy with infrared excitation. The authors demonstrate the ability to launch and detect propagating optical plasmons in tapered graphene nanostructures, providing real-space images of plasmonic field profiles. They find that the extracted plasmon wavelength is significantly shorter than the illumination wavelength, over 40 times smaller. This strong optical field confinement allows the graphene nanostructure to act as a tunable resonant plasmonic cavity with an extremely small mode volume. The cavity resonance is controlled in-situ by gating the graphene, enabling complete switching on and off of the plasmon modes. This work paves the way for the development of graphene-based optical transistors and other nano-optoelectronic devices, offering unprecedented active subwavelength-scale optics and enhanced light-matter interactions for quantum devices and biosensing applications.