In living cells, membrane receptors transduce ligand binding into signals that initiate proliferation, specialization, and secretion of signaling molecules. Spatial organization of such receptors regulates signaling in several key immune cell interactions. In the most extensively studied of these, a T cell recognizes membrane-bound antigen presented by another cell, and forms a complex junction called the "immunological synapse" (IS). The importance of spatial organization at the IS and the quantification of its effect on signaling remain controversial topics. Researchers have successfully investigated the IS using lipid bilayers supported on solid substrates as model antigen-presenting membranes. Recent technical developments have enabled micron- and nanometre-scale patterning of supported lipid bilayers (SLBs) and their application to immune cell studies with provocative results, including spatial mutation of the IS. In this tutorial review, we introduce the IS; discuss SLB techniques, including micropatterning; and discuss various methods used to perturb and quantify the IS.