To create an intricately patterned and reproducibly sized and shaped organ, many cellular processes must be tightly regulated. Cell elongation, migration, metabolism, proliferation rates, cell–cell adhesion, planar polarization and junctional contractions all must be coordinated in time and space. Remarkably, a pair of extremely large cell adhesion molecules called Fat (Ft) and Dachsous (Ds), acting largely as a ligand–receptor system, regulate, and likely coordinate, these many diverse processes. Here we describe recent exciting progress on how the Ds–Ft pathway controls these diverse processes, and highlight a few of the many questions remaining as to how these enormous cell adhesion molecules regulate development.