The control of organ size growth Is one of the most fundamental aspects of life.In the past two decades,a highly conserved Hippo signaling pathway has been identified as a key molecular mechanism for goveing organ size regulation.In the middle of this pathway is a kinase cascade that negatively regulates the downstream component Yes-associated protein(YAP)/transcriptional coactivator with PDZ-binding motif(TAZ)/Yorkie through phosphorylation.Phosphorylation of YAP/TAZ/Yorkie promotes its cytoplasmic localization,leads to cell apoptosis and restricts organ size overgrowth.When the Hippo pathway is inactivated,YAP/TAZ/Yorkie translocates into the nucleus to bind to the transcription enhancer factor(TEAD/TEF)family of transcriptional factors to promote cell growth and proliferation.In this review,we will focus on the structural and functional studies on the downstream transcription factor TEAD and its coactivator YAP.