Communication between neurons happens primarily through chemical neurotransmission at the synapse. Neurotransmitters are packaged into synaptic vesicles for release from the presynaptic cell into the synapse, from where they diffuse and can bind to postsynaptic receptors. While most presynaptic cells are historically thought to release one vesicle  at a time per active site,  more recent research has pointed towards the possibility of multiple vesicles being released from the same active site (multivesicular release; MVR) in response to an action potential.