Cover picture: In this issue, Sobczyk et al. measure NMDA receptor (NMDA-R)-mediated Ca2+ signaling in individual hippocampal dendritic spines. Using a combination of two-photon Ca2+ imaging, glutamate uncaging, and whole-cell recordings, they found that the amplitude of Ca2+ transients in spines depends on the subunit composition of synaptic NMDA-Rs. The cover shows a single dendritic spine composed of many two-photon images of CA1 pyramidal neurons used in this study. For details, see pages 6037–6046).