Lipid molecules have split personalities—one part loves water, whereas the other avoids it at all costs. Lipids make up cell membranes, the frontline defense in preventing cellular access to bacterial and viral invaders. Many researchers believe that the membrane is not just a scaffold where proteins reside, but instead actually plays an important role in a number of biological processes. Researchers are also starting to see that lipids and proteins can form small patches, similar to a mosaic. This patchiness seems to have a functional role in the life of a cell and in regulating its different processes. Functional patches of lipids are commonly referred to as lipid rafts.