The morpho-functional organization of secretory traffic. Here today, where tomorrow?

The morpho-functional principles of secretory traffic are still unclear, in stark contrast with our advanced knowledge of the underlying molecular machineries. Recently, the conceptual and technological hindrances that have delayed progress in this area have been disappearing, and new glimpses of the organization of traffic in intact cells are being revealed by a cluster of powerful morphological techniques. Here, we discuss the new advances in the light of the three main possible traffic principles: by anterograde vesicles, progression/maturation, and flow via continuities.