Use-dependent synaptic potentiation and depression are thought to underlie memory formation in the mammalian brain. One pathway for long-term depression is mediated by calcium influx through NMDA receptors, which triggers AMPA-type glutamate receptor endocytosis. I have developed two techniques in electron microscopy; “Flash-and-freeze” electron microscopy (EM) combines optogenetic neuronal stimulation (“flash”) with rapid, high-pressure freezing (“freeze”) to capture endocytosis on a millisecond timescale; nano-fEM combines super-resolution fluorescence microscopy with EM to visualize fluorescently tagged proteins within their sub-cellular context. Using these techniques, I will test how AMPA receptors are endocytosed from the surface.