Hydrocolloids describe certain chemicals (mostly polysaccharides and proteins) that are colloidally dispersible in water. Thus becoming effectively "soluble" they change the rheology of water by raising the viscosity and/or inducing gelation. They may provide other interactive effects with other chemicals, in some cases synergistic, in others antagonistic. Using these attributes hydrocolloids are very useful chemicals since in many areas of technology from foods through pharmaceuticals, personal care and industrial applications, they can provide stabilization, destabilization and separation, gelation, flow control, crystallization control and numerous other effects. Apart from uses of the soluble forms some of the hydrocolloids have additional useful functionality in a dry form if after solubilization they have the water removed - as in the formation of films for breath strips or sausage casings or indeed, wound dressing fibers, some being more compatible with skin than others. There are many different types of hydrocolloids each with differences in structure function and utility that generally are best suited to particular application areas in the control of rheology and the physical modification of form and texture. Some hydrocolloids like starch and casein are useful foods as well as rheology modifiers, others have limited nutritive value, usually providing a source of fiber.