The Shen laboratory studies the neuronal cell biological questions using the nematode C. elegans as a model system. We have studied in vivo synapse formation and synaptic specificity by labeling defined synapses in single cell resolution and performed forward genetic screens to identify genes required for synapse formation and synaptic target selection. In the recent years, we have also extensively studied the molecular mechanisms of dendrite branching. Through forward genetics analysis, we have identified a ligand receptor complex that is specifically required for dendrite branching but not for axon development. This complex contains three ligands that are made from two tissues, skin and muscle. The dendrite receptor is only activated when all three ligands are presents. The coincidence detection afforded by this complex precisely targets the sensory dendrite to innervate the space between muscle and skin. We have also identified several mechanisms that regulate dendrite morphology during development and by environment through controlling the level of the receptor. We have also established molecular tools to systematically study the organization of microtubules in neurons. This series of genetic and cell biological studies has provided insights of sensory dendrite morphogenesis.