Over the last years, the analysis of synaptic connectivity in the mammalian brain has been accelerated by the use of techniques combining electrophysiology, light microscopy, viral tracing, and genetic manipulations in animal models. Of particular interest are methods that aim to label synapses by tethering complementary split GFP fragments in opposing sites of the synaptic cleft. Here, I describe SynView, a method for monitoring synapse formation based on GFP complementation and provide a detailed protocol for use in neuronal cultures from mouse hippocampus.