The mature brain results from the formation of precise networks between functionally and morphologically distinct types of neurons. A given neuron forms synapses with a limited number of partners and on precise subcellular localizations. Understanding what controls this specificity is mandatory not only to understand brain functions but also the etiology of synaptopathies such as autism spectrum disorders or schizophrenia. Various molecules define the identity of each type of synapse. Furthermore, neuronal activity- dependent mechanisms sculpt and stabilize neuronal connectivity. Our team’s work aims at dissecting how neuronal activity controls the molecular identity of synapses with the postulate that this regulation occurs through mechanisms specific for each neuronal population, thereby regulating synapse specificity. We focus on the olivocerebellar network, which is involved in motor control and also in cognitive processes.