Coordinated rearrangement of cell membrane receptors into large-scale patterns is emerging as a broadly significant theme of intercellular signal transduction. In an effort to help unravel the mechanisms governing protein organization at intercellular synapses and the role of this organization in signal transduction, we have dissected living T cell immunolgical synapses in a hybrid live cell - supported membrane configuration. Nanometer-scale patterns of fluid lipid membranes, displaying cell recognition and signaling molecules, have been constructed on solid substrates by a combination electron-beam and scanning-probe lithographic techniques, along with membrane self assembly. When doped with appropriate proteins, supported membranes mimic and antigen presenting cell and can form synapses with living T cells. The substrate nanostructures guide the mobility of membrane-linked proteins and, correspondingly, the motion of their cognate partner proteins within living cells. A critical feature of this strategy is that proteins displayed in the supported membrane exhibit diffusive mobility. This enables formation of functional synaptic structures with living cells by permitting the necessary protein rearrangements. The manner in which precisely defined geometrical restrictions frustrate or facilitate synapse formation and signaling in living cells can be used to elucidate the mechanisms and functional consequences of molecular patterns at intercellular synapses.