Homogenization is a process that keeps different parts of a food from separating. Basically, it uses pressure and agitation to break up particles so they become better mixed with other particles and don't stick to each other, or separate. Examples include milk and peanut butter. In the case of peanut butter, the oils normally separate from the solids. An all natural peanut butter must be mixed if allowed to stand for a long period of time. A homogenized peanut butter won't need to be re-mixed, but the physical characteristics of the particles and nutrients are changed, with potential side effects on taste and nutrition.