This book concerns colloidal dispersions in which dispersed phase is encapsulated in a soap film (Alphrons). The principle examples are foams and biliquid foams. Many applications of these are possible, and many of these are discussed, for example, removal of trace substances from water, predispersed solvent extraction and safety fuels. The concepts can also be useful in biology to enhance understanding of the structure of biomembranes and adhesion between cells. The book is interdisciplinary in approach, and many different fields will be interested in the new concepts outlined.