Bacterial cell division is mediated by the divisome which is organized by the Z ring, a cytoskeletal element formed by the polymerization of the tubulin homologue FtsZ. Despite billions of years of bacterial evolution, the Z ring is nearly universal among bacteria that have a cell wall and divide by binary fission. Recent studies have revealed the mechanism of cooperative assembly of FtsZ and that the Z ring consists of patches of FtsZ filaments tethered to the membrane that treadmill to distribute the septal biosynthetic machinery. Here, we summarize these advances and discuss questions raised by these new findings. The Z ring is discontinuous and consists of patches of FtsZ assemblies that treadmill circumferentially at the division site.The mechanism of FtsZ treadmilling was revealed by determination of the conformational changes that accompany assembly and the kinetic polarity of FtsZ filaments.FtsZ employs an intrinsically disordered linker and a molecular recognition motif (MoRF) to achieve flexibility and avidity in tethering FtsZ filaments to the membrane.Evidence exists that crosslinking and bundling of FtsZ filaments contribute to assembly of the Z ring, but how filaments are organized in patches awaits further investigation.Treadmilling FtsZ filaments are coupled to the septal PG machinery through membrane anchors.