The molecular mechanisms that link intracellular signalling pathways to changes in tissue morphology are unclear. Using the Drosophila embryonic hindgut as a model, Martin Zeidler and co-workers demonstrate that the transmembrane protein Fasciclin III (FasIII) regulates intracellular adhesion and links signal transduction to morphogenesis (p. 3858). The researchers show that normal hindgut curvature is dependent on JAK/STAT signalling, and that JAK/STAT pathway activity asymmetrically localises to the inside curve of the developing hindgut, where it drives FasIII lateralisation. In addition, they demonstrate that FasIII promotes intracellular adhesion both in vivo and in cells in vitro. Based on these findings and the differential interfacial tension hypothesis, the researchers establish a mathematical model of the developing hindgut, which suggests that intracellular adhesion mediated by FasIII is sufficient to explain the curvature observed in the hindgut. These findings, together with additional studies of tissue folding in the Drosophila wing disc, suggest that FasIII-dependent modulation of intracellular adhesion might be a general mechanism by which organs are shaped during development.