Microfluidic devices can be used for either pre-mix emulsification (a method in which a coarse emulsion is broken up by passing it through a geometry) or direct emulsification (a method in which oil and water are introduced separately in the device and the emulsion is formed at their point of contact). Depending on the surface properties of the microfluidic device or other microstructured device (e.g. membrane) either oil-in-water (hydrophilic device) or water-in-oil (hydrophobic device) emulsions are formed. Also related products, such as double emulsions, particles and capsules are reported in literature. For an extensive description of the construction of various microfluidic devices for emulsion preparation, and the various products that have been reported, please consult the recent comprehensive review by Vladisavljevic, Kobayashi, and Nakajima . For further reading also the review on droplet based microfluicics by Seeman and co-workers  is highly recommended. In the current chapter, the most used microfluidic devices are described, and compared using criteria based on scaling relations, ease of operation and productivity. In the future research section, the use of these devices as tools for dynamic interfacial tension measurement, and emulsion stability are discussed amongst others.