Cover legend: Electron micrograph of an SDS-digested freeze-fracture replica immunolabeled with an antibody that recognizes all subunits of AMPA-type glutamate receptors (pan-AMPA). The micrograph illustrates a presynaptic axon terminal and its postsynaptic membrane specialization (intramembrane particle cluster) that shows strong immunoreactivity for pan-AMPA. The AMPA receptor subunits are labeled with 5 nm gold particles. For more information, see the article by Antal et al. in this issue (pages 9692–9701).