The plasma (outer) membrane of living cells is a dynamic 2-D fluid of embedded mobile and immobile objects (proteins) with a sub-surface scaffolding (the membrane skeleton) and a forest of sugars and secreted proteins on the extracellular surface. We are applying single molecule imaging techniques to help elucidate the fine structure of this complex system. I will discuss observations of the free diffusion of individual membrane molecules (at video rates up to 40500 frames/sec!) revealing an anomalous motion that implies a compartmentalized, mosaic structure in the fluid membrane. Further, by applying a subtle hand (optical tweezers) to move the constituents around, we have force-imaged this structure using a transmembrane protein as a scanning probe “tip”. Implications of this to maintenance of cell polarity in neuron cells and cellular signaling will be presented.