During the development of neural circuits, excessive synapses are formed in a genetically programmed manner. Neural circuits are refined by the experience dependent pruning of supernumerary imprecise connections and the strengthening of the functional synapses. The molecular mechanisms underlying this process remain largely unknown. In [1], authors describe the role of ephrin-A2 in regulating experience dependent, NMDA-receptor mediated synaptic pruning through glial glutamate transport during maturation of the mouse cortex.