The constitution of advanced reverse micelles is important to realize idealized separation process of proteins. Reverse micelles composed of ionic surfactants have been commonly used for separation of proteins. However, they have essential disadvantages for this purpose, i.e., denaturation and inactivation of proteins, and unsuitability for selective separations. Control of the electrostatic interactions between proteins and ionic surfactants makes it possible to extract proteins and to reduce denaturation of proteins significantly. This is realized by changing the composition of surfactants constituting reverse micelles, that is, the use of reverse micelles mainly composed of nonionic surfactants with minimum amount of ionic surfactants. When affinity ligands, which can recognize a target protein, are incorporated to reverse micelles composed of a nonionic surfactant, the selective separation of a target protein can be achieved. Highly functional systems can be constituted by tailoring reverse micellar systems for the required aims.