Emulsification is a powerful, well-known technique for mixing and dispersing immiscible components within a continuous liq. phase. Consequently, emulsions are central components of medicine, food and performance materials. Complex emulsions, including Janus droplets (i.e., droplets with faces of differing chemistries) and multiple emulsions, are of increasing importance in pharmaceuticals and medical diagnostics, in the fabrication of microparticles and capsules for food, in chem. sepns., in cosmetics, and in dynamic optics. Because complex emulsion properties and functions are related to the droplet geometry and compn., the development of rapid, simple fabrication approaches allowing precise control over the droplets' phys. and chem. characteristics is crit. Significant advances in the fabrication of complex emulsions have been made using a no. of procedures, ranging from large-scale, less precise techniques that give compositional heterogeneity using high-shear mixers and membranes, to small-vol. but more precise microfluidic methods. However, such approaches have yet to create droplet morphologies that can be controllably altered after emulsification. Reconfigurable complex liqs. potentially have great utility as dynamically tunable materials. Here we describe an approach to the one-step fabrication of three- and four-phase complex emulsions with highly controllable and reconfigurable morphologies. The fabrication makes use of the temp.-sensitive miscibility of hydrocarbon, silicone and fluorocarbon liqs., and is applied to both the microfluidic and the scalable batch prodn. of complex droplets. We demonstrate that droplet geometries can be alternated between encapsulated and Janus configurations by varying the interfacial tensions using hydrocarbon and fluorinated surfactants including stimuli-responsive and cleavable surfactants. This yields a generalizable strategy for the fabrication of multiphase emulsions with controllably reconfigurable morphologies and the potential to create a wide range of responsive materials. [on SciFinder(R)]