Nanoscale electron transfer (ET) in solids is fundamental to the development of multifunctional materials. However, ET in solids is not yet clearly understood. Now, researchers achieved a direct observation of solid-state ET through X-ray crystal analysis by fabricating a novel double-walled non-covalent crystalline nanotube, which can absorb electron donor molecules and maintain its crystalline structure during ET. This innovative approach can lead to the design of novel functional materials soon.