Simultaneous lipid and content mixing assay of small unilamellar vesicles (SUV) and giant unilamellar vesicles (GUV). Confocal microscopy images of GUVs labeled with Rh-1,2-di-(9Z-octadecenoyl)-sn-glycero-3-phosphoethanolamine (DOPE) (red) and large unilamellar vesicles (LUV) labeled with NBD-DOPE (green) containing sulforhodamine at self-quenching concentration. In Upper, we use two different lasers with wavelength corresponding to the excitation wavelength of NBD and Rho to excite the different fluorophores. In contrast, in Lower, only the excitation wavelength of NBD is used to obtain FRET. Each collection of four images is a different GUV representative of the situation indicated in the labels after 20 min of incubation. (Scale bars, 10 μm.)