A new liquid-liquid extraction method, called the "emulsion-flow" method, has recently been developed at Japan Atomic Energy Agency (JAEA). The emulsion-flow method, where low cost, simplicity, high efficiency, compactness, safety, and eco-friendly go together, has attracted attention, and has been expected to bring innovation to liquid-liquid extraction technologies. An apparatus based on the emulsion-flow method can actualize very efficient liquid-liquid extraction with its high two-phase mixing ability to an emulsion by spraying micrometer-sized oil droplets into a counter-current aqueous solution by only solution sending. Meanwhile, at the same time, the emulsion produced in the apparatus disappears rapidly and perfectly by drastically changing the cross-section where liquid droplets pass through in its vessel structure. Such a rapid and perfect phase separation can realize a high processing speed with a small sized apparatus. Compared with conventional industrial apparatuses, an emulsion-flow apparatus successfully combines the lowest cost superior to a spray column and the highest performance (the highest efficiency and the highest processing speed) comparable to a centrifugal extractor. Furthermore, the emulsion-flow method can also be used for collecting particulate components by utilizing their aggregation onto a liquid-liquid interface and for purifying water polluted by oil with its remarkable phase-separating ability.