Cilia are anchored to the cell membrane by distal and sub-distal appendages (grey and green triangles) in the basal body. The Y-links (light blue) in the transition zone gate at the base controls the entry of proteins into the cilium. Proteins (brown hexagons), transmembrane proteins (brown) and other cargo are transported along microtubule tracks (grey cylinders) from the base of the cilium to the tip by kinesin motor proteins (blue) and an IFT train (yellow). The cargo proteins are attached directly to the IFT train or via cargo adaptors (brown ovals). At the tip, the trains release their cargo and break apart before remodeled IFT trains are returned to the base by dynein (pink). Kinesin, on the other hand, diffuses back to the base. Using a new imaging technique called PhotoGate, Chien et al. labeled certain proteins with fluorescent molecules, and then used a laser to 'photobleach' most of them (represented here by fading) before they reached the tip. Since the photobleached molecules are dark, it is possible to follow the small number of labeled trains that remain fluorescent, and to better track their behavior at the tip of the cilium in order to study the remodeling of IFT trains.