New technologies for imaging synaptic partners.

Understanding the brain will require unraveling its synaptic circuitry, but methods that can reliably identify connected neurons are often excruciatingly slow. Although light microscopy can provide much higher throughput, synapses are smaller than the diffraction limit and cannot readily be assigned to particular presynaptic and postsynaptic cells without specialized labeling methods. Here we review the ongoing development of techniques that allow direct imaging of neural networks by specifically marking connected cells or their synapses.