In order to fully characterize the repartition of the components in the double emulsions, we synthesized fluorescent PEG from diamino-PEG derivative using FITC (see materials and methods) and mixed this dye with octanol-PEG to be further poured in hot PVA. The resultant double emulsion showed droplets having a highly fluorescent core, surrounded by a nonfluorescent shell, all in a very slightly fluorescent background (figure ). In parallel, when sulforhodamine B was initially dispersed in PVA, the resulting double emulsion (prepared without using PEG-FITC) showed droplets lacking fluorescence, all embedded in a continuous highly fluorescent background (figure ), meaning that the chemicals initially dispersed in the continuous water phase are not recovered in the droplets.