The composition and identity of cell organelles are dictated by the flux of lipids and proteins that they receive and lose through cytosolic exchange and membrane trafficking. The trans-Golgi network (TGN) is a major sorting centre for cell lipids and proteins at the crossroads of the endocytic and exocytic pathways; it has a complex dynamic structure composed of a network of tubular membranes that generate pleiomorphic carriers targeted to different destinations. Live-cell imaging combined with three-dimensional tomography has recently provided the temporal and topographical framework that allows the assembly of the numerous molecular machineries so far implicated in sorting and trafficking at the TGN.