The main goal of the ongoing research in my laboratory is to study the involvement of glial cells in the regulation of synaptic activity and properties. We use various imaging techniques coupled to electrophysiological recordings of neurons, glial cells and synaptic activity. I will discuss recent data illustrating the regulation of synaptic activity by glial cells at the level of single CNS synapses. A new perspective of the chemical synapse has emerge from our work whereby the perisynaptic glial cells are considered active partners of the synapse and gave rise to the concept of the "tripartite synapse" which includes the presynaptic and the postsynaptic elements and the perisynaptic glia.