Formation of glutamatergic synapses involves development of “silent” immature contacts into mature functional synapses. To understand how this transformation occurs, I am investigating the development of neurotransmission at single synapses in vitro. Using single synapse stimulation to induce endogenous release, while simultaneously probing the function of postsynaptic receptors of the same synapse, has provided a powerful and unique method to determine how the pre- and postsynaptic attributes of synapses mature. Using these recently developed techniques I have shown that the phenomena of “silent” transmission can occur at synapses which demonstrably contain functional AMPA receptors, contrary to previous views. Our work has revealed that maturation of synaptic transmission consists of an enhancement in the flux of transmitter delivery into the cleft, transforming “presynaptically silent secretion” into mature synaptic transmission.