Cover legend: Surface neurotransmiter receptors, such as AMPA and NMDA receptors, transmit fast information between neurons. One way to investigate receptor surface trafficking is to use the single-molecule/particle detection method. The principle is based on the detection of single nanometer-sized molecules (e.g., organic dyes) or particles (e.g., Dots) that are coupled to surface receptor through a specific antibody. The cover image represents a hippocampal cultured neuron (with artistic distortion) that has been labeled with the synaptic marker Mitotracker (white spots) and an anti-GluR2 antibody (subunit of the AMPA receptor) coupled to QDots (green spots). Each of the green spots represent a single Dot at a given time point. Labeling must be performed at low tag densities in order to be optically resolved. QDot–GluR2 complexes are detected both outside and in synapses. Thanks to François Georges for artistic design of the image. For more information, see the Toolbox article by Groc et al. in this issue (pages 12433–12437).