Previously, fluorescence imaging has been used simultaneously with resistive-pulse sensing for studies of single passed fluorescently labeled DNA, H2 formation on single freely diffusing photoactive 40 nm Ag nanoparticles, and single passed fluorescent PS nanoparticles 2 m in diameter. Yu et al. used fluorescent PS nanoparticles (diameter = 260 and 540 nm) to track the Brownian motion of nanoparticles upon exiting a nanopipette. In this latter study, an external excitation light source was used to illuminate nanoparticles to obtain the diffusional paths outside of the nanopipette, where limited pressure-driven particle multipassing was reported in order to obtain multiple diffusional paths of the same particle. In our current study of fluorescently labeled liposomes, the excitation light is delivered through the cleaved end of a single-mode optical fiber located within the nanopipette (positioned ~1 mm from the nanopipette orifice) to illuminate the liposomes inside the nanopipette (Figure ). The nanopipette is filled with electrolyte solution and an internal Ag/AgCl electrode is placed inside of the nanopipette. The illuminated tip of the nanopipette is submerged in the electrolyte solution and positioned above the objective of an inverted microscope. This scheme takes advantage of the waveguide properties of the nanopipette to automatically direct illumination to the tip and thus does not suffer from fluctuations in excitation intensity at the small tip due to mechanical drift or vibration of the nanopipette relative to the position of external illumination source. A second external Ag/AgCl is placed in the bulk electrolyte solution exterior to the nanopipette. The potential of the external Ag/AgCl electrode is alternated between positive and negative potential (typically ±1 V) with respect to the internal electrode to drive liposome multipassing. The fluorescence emission (≥ 500 nm) of the DiO molecules within the liposome membrane is recorded during multipassing. A photograph of the experimental setup is shown in the Supporting Information (Figure ).