Epithelial tubes arise as short buds, and during mid-embryogenesis they undergo dramatic transformations, elongating and narrowing. This process occurs in the absence of cell proliferation and is accompanied by cell rearrangements. Saxena et al. used fly renal tubules to investigate the mechanism driving such transformations and found that elongation results from polarized cell intercalation that leads to a decrease in cell number around the lumen and an increase in tube length. Oriented cell intercalation is directed by epidermal growth factor (EGF) signalling from specific cells that are located at the distal tubule tip. The resulting acquisition of planar cell polarity causes the asymmetrical accumulation of the motor protein myosin II in the basal cell cortex, and pulsatile and polarized cell contraction, which enables cell movement.