Synaptic plasticity, meaning changes in structure and/or function of the synaptic connections between neurons, is a cellular basis of learning and memory processes in the brain. Particularly, the formation of new, additional synapses within neuronal circuits is considered to be a primary mechanism for long-term synaptic plasticity. However, the elementary mechanisms controlling functional and structural assembly of synapses remain understood only very poorly. Aim of our laboratory is to study synaptic assembly and remodeling processes in intact living preparations, particularly concentrating on the relation between structural and functional organization.