Cell membranes are two-dimensional heterogeneous fluid surfaces comprised of lipids, proteins, and carbohydrates. Understanding their organization at the molecular level is of critical importance for understanding cellular function. One of the key features, of the cell membrane is it's fluidity, which precludes long range order. However, due to the heterogeneous nature of the system it is possible that non-uniform mixing occurs, resulting in the local enhancement of certain membrane components. We will present results from our studies designed to probe for one type of domain, termed 'lipid rafts', using model membranes. In particular, we use supported lipid bilayers that are partitioned; the partitioning enables us to spatially contain the membrane components. By applying an electric field in the plane of the bilayer we can rearrange the membrane components in the partitioned regions. Sphingolipids and cholesterol, the major components of lipid rafts are electrically neutral and will not reorganize in response to a field; however, GM@sub 1@, a minor component, will as it has a net negative charge. Using epi-fluorescence microscopy we monitored the resultant electric field induced reorganization of the membrane components. Our results indicate that the reorganization of the GM@sub 1@ induces a reorganization of the sphingolipids and cholesterol. However, this reorganization does not appear to be concerted, suggesting that the rafts are not long-lived structures. That is, there is an increased propensity for certain components to be in close proximity to one another, but due to the fluid nature of the lipid bilayer, individual components are not in close proximity for long. This work will hopefully provide additional insight into understanding how non-uniform mixing occurs in these fluid surfaces and what the functional consequences are.