The general preparation technique and characteristic behaviors of oil-in-water-in-oil and water-in-oil-in-water type multiple emulsions were described. For the preparation technique, the advantages and disadvantages of the single step procedure and double step procedure were discussed. The formulations for stable multiple emulsions and the assessment of their stability was described. The results of authors experiments, the stabilization of an unstable agent in the innermost phase and the studies of characteristic texture of O/W/O type multiple emulsion were also described here.

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In our daily lives, skin-care cosmetics play important roles in regulating the skin condition and they are required to show various functions, such as moisturizing effect, emollient effect, or antiaging effect, etc. These demands have led the developments of new oil materials and emulsifiers (or emulsification techniques) which should be available to make the modern skin care formulations.
In this summary, we describe the recent results of innovations, including (1) ceramides and ceramides based formulations, (2) macadamia nut oil derivatives and (3) new lipohilic pro-vitamin C as the new oil materials, and (1) the utilization of self-organization property of surfactants (2) polyglycerine fatty-acid esters (3) polymeric emulsifiers and (4) lecithin and lecithin derivatives as the new emulsifiers and emulsification techniques.

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Various kinds of oil which can keep our skin emollient are widely used in cosmetic formulations. It is technically important to make oil into a gelling state in order to improve stability of cosmetic products. Dimethylpolysiloxane has become popular recently, because it has unique properties, such as smooth and non-greasy touch and water repellency. However, oil gelling agents, particularly a gelling agent of dimethylpolysiloxane are less found in cosmetic ingredients.
Thus, the cross-linked polysiloxane which can swell in dimethylpolysiloxane forming a soft gel has newly been developed. Then modifying the above cross-linked polysiloxane made it possible to make oil, such as paraffins, esters, glycerides into a stable gel, and W/O type gel emulsions can also be obtained. In this paper, the structure and characteristics of the cross-linked polysiloxane are introduced together with some examples of cosmetic applications.

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The basic role of skincare formula is moisturization of skin controlling with suitable feeling. Natural moisturizing factor, sebum, and ceramide are nessesary for keeping healthy skin. Skincare products have a role to supply them into stratum corneum. These days study of dermatology is advanced remarkably. Many preventive or treating materials for aging problem of skin; wrinkle, pigmentation etc. are found. Therefore, it becomes more important for skincare product to penetrate them into suitable position of the skin. Skin penetration enhancers are synthesized and mechanical penetration systems are made. But they are not suitable as a cosmetic, because it is not always safety and a simple and easy way. New skincare formula are developed and their characters are investigated. Microemulsion is prepared by physicochemical or mechanical methods. This is transparence and much stable. Additionally, enhance of penetration of materials are expected.

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