This Chapter focuses on the design and engineering of injectable submicronic fluorocarbon emulsions designed for in vivo oxygen transport. It reviews the basic principles that are relevant to this objective, and discusses the selection of component fluorocarbons and emulsifiers, the formulation and preparation of the emulsions, and the properties of typical emulsions, with special emphasis on stability and biocompatibility. The ability of fluorocarbons to carry and deliver the expected amount of oxygen has been demonstrated with the first generation emulsions. The gas-dissolving capacity of fluorocarbons stems essentially from the weakness of the intermolecular cohesion forces in the liquid. Preparation of fluorocarbon emulsions involves the dispersion of the fluorocarbon into submicron droplets in a continuous saline phase in the presence of the surfactant. Gelifying fluorocarbons is, a priori, quite a challenge. Fluorocarbons are indeed extremely fluid and mobile liquids as a consequence of very weak intermolecular cohesive forces, and they do not dissolve the usual gelifying agents.