While the structures of several G protein coupled receptors (GPCRs) have been solved by X-ray crystallography, the high-resolution structure of first ligand-gated ion channels (LGICs) has been available only recently. The ultrastructure of the prototypic LGIC nAChR is deduced from electron microscopy in combination with crystal structures of model proteins. From this analysis, agonist and antagonist binding sites and hints at the mechanism of channel gating become visible.