Hippo signaling pathways control diverse aspects of cell proliferation, survival, and morphogenesis in eukaryotes. The core organization of these networks is conserved over a billion years of evolution, with related forms described in animals and fungi. In Drosophila and mammals, Hippo/MST co-operate with Mats/Mob1 and Salvador/WW45 to activate Warts/LATS, which negatively regulates Yorkie/YAP. Yorkie/YAP interact with Scalloped/TEAD to promote gene transcriptions and control organ size through the balance between cell proliferation and apoptosis. In C. elegans, WTS-1 YAP-1 EGL-44 axis is conserved and regulates thermotolerance and healthy lifespan. In S. cerevisiae, the LATS-related Dbf2 or Dbf20 kinase in complex with Mob1 controls mitotic exit and cytokinesis, and the Hippo/MST family of kinases, STE-20, modulates Tec1, the putative yeast TEAD ortholog.