The release of neurotransmitters and hormones is mediated by exocytosis, that is the fusion of vesicles which contain those substances with the cellular membrane. We are interested in the cellular and molecular mechanisms which control and trigger this process, since they are responsible for the communication among neurons, as well as for a variety of other signaling mechanisms in our body. We specialize on problems of synaptic short-term plasticity, on factors governing the availability of secretory vesicles, as well as on developmental aspects of synaptic transmission. Advanced optical tools are used to study the dynamics of synaptic vesicles within nerve terminals. An independent group studies retinal ganglion cells in primates, in order to obtain insight into higher aspects of signal processing in the visual system, particularly with respect to color vision.