Intracellular trafficking of ammoniumn-functionalized single-walled carbon nanotubes reveals that after cell internalization the nanotubes translocate around the cell nucleus of human lung carcinoma cells (A549). The luminescent signal of the carbon nanotubes (no fluorescent labels) is used for 3D intracellular tracking (see figure). The presented methodology is expected to offer a widely usable tool that will further elucidate the intracellular transport mechanisms of carbon nanotubes.