In order to induce osmose diffusion of water into oil droplets, we first dispersed PEG (20 kDa at 2.5, 5 and 10%) in 1-octanol by heating and shaking samples at 80°C to fully solubilize the polymer. We observed that these oily transparent liquid solutions gelled when cooling. This was determined by visual inspection by decreasing the temperature of a hot sample tube or by increasing the temperature of a sample initially at RT (figure ) This was quantitatively investigated by rheological oscillatory measurements. Ramps of temperatures were performed at a fixed amplitude (5%) and frequency (1Hz). In the gel phase, an elastic modulus was measured, and it vanished at high temperature. Note that different behaviors are found under cooling and heating (figure ). Still, we can well identify a crystallization temperature, under cooling, of T= 40 °C. Emulsification procedure was then performed at 70°C, except when mentioned. An oil-inwater (O/W) emulsion was then prepared by pouring hot PEG-octanol dispersions (300 µL) in an aqueous polyvinyl alcohol solution (PVA, (Mowiol 4-88, 31 kDa), 10%, 2 mL, 70°C), which is a polymer often used to stabilize emulsions . Except when mentioned, the volumes of both the oily phase and aqueous PVA were the same for all sample preparations. The use of Nile red initially dispersed in octanol-PEG allowed detection of this apolar phase by epifluorescence. We first observed that PEG-free octanol-in-PVA stable emulsions were formed with single octanol droplets embedded in the aqueous continuous PVA-rich phase (figure ). Upon increasing the amount of PEG initially dispersed in 1-octanol, droplets appeared within the oily droplets. These internal droplets lacked fluorescence confirming that aqueous droplets were formed within oil (figure ). At low amount of PEG (2.5%), few droplets were observed within oil droplets (figure ), forming multiple-core emulsions. At 5% PEG, the number and diameter of aqueous droplets within oil droplets increased, forming both multiple-and single-core double emulsion droplets (figure ). An ideal single-core double emulsion was obtained for 10% PEG initially dispersed in 1-octanol with mainly a single aqueous droplet within oily ones (figure ). Right: epifluorescence images (A-D) for emulsions produced with x = 0, 2.5, 5 and 10 % PEG in 1-octanol, respectively. Scale is the same for all images and stands for 20 µm.