Astrocyte plays a crucial role in neuronal synaptic formation. However, our understanding of astrocyte-neuron interaction is hindered by the lack of in vivo cell-cell interaction proteome technique. Recently, a paper published in Nature by Cagla Eroglu and Scott H. Soderling et al. reported a Split-TurboID method[1] , utilizing a in vivo chemico-genetic approach to identify the proteome between the astrocyte-neuron cleft. Among these proteins, they found the astrocytic NrCAM negatively regulates astrocyte territory size and neuropil infiltration volume via transmembrane homophilic interaction with neuronal NrCAM. In addition, this interaction promotes inhibitory synaptic formation with the participation of gephyrin.