Physiological roles for postsynaptic molecules in synaptogenesis and plasticity are under intense investigation. Recent imaging experiments, including GFP-based and single-particle tracking strategies, reveal rapid movement of synaptic components to and from the postsynaptic sites. Furthermore, specific patterns of neuronal activity and/or activation of specific transmitter receptors trigger selective translocation of postsynaptic components. These emerging dynamic properties of synaptic specializations add another layer of complexity to the signaling mechanisms of CNS synapses.