Fluorescence emission spectroscopy exploits the physical phenomenon of excited-state energy emission and is widely used in many fields due to its low detection limit. This technique allows the presence of species at very low concentrations to be determined in several media types. Such species must emit light at a certain wavelength, which a spectrofluorometer can then record. If the species to be investigated are not fluorescent, a fluorophore, such as HPTS, can be used to detect their presence in solution or monitor certain processes triggered by them. Although the Gale and Quesada research groups use different fluorescence spectrophotometers: an Agilent Cary Eclipse, a HORIBA Scientific Fluoromax 4, and a Hitachi F-7000, any spectrofluorometer may work as long as it can detect the fluorescence at the wavelength of interest (510 nm). However, to ensure consistency, the fluorometer must be equipped with a cell holder with a magnetic stirrer function, a temperature controller, and connected to a computer. Also, to ensure the homogenous distribution of vesicles in solution, a moderate stirring rate should be maintained during the experiments and conducted at a consistent temperature (usually 25 ℃ (298 K)). In this way, the obtained data will be comparable. Like any instrument, fluorescence spectrophotometers require maintenance and must be kept clean (especially the cell or multi-cell holder) to avoid dust accumulation and subsequent interference. The lamps should also be changed when reaching the limit of their lifetime (the equipment's software usually informs the user through an alert when the time has come; otherwise, please refer to the manual of the lamp's supplier).