We will present new and as yet unpublished work that provides new insights into signaling at neuronal synapses.One area of research focuses on the existence and functional meaning of multiple modes of synaptic vesicle fusion triggered by Ca2+.The opening of Ca2+ channels drives at least two distinct forms of fusion.In the classical mode,known as "full collapse fusion",the vesicle membrane fully merges with and flattens into the presynaptic membrane.In a newly characterized mode,termed "kiss-and-run" the connection between the vesicle interior and the external medium lasts long enough to allow passage of neurotransmitter,but the connection is severed before the identity of the vesicle is lost.