Two-color, time-resolved labeling enables visualization of O-glycan trafficking. Zebrafish embryos were microinjected with GalNAz, allowed to develop to 9 hpf, and reacted with DIFO-488 (100 μM, 1 h). The embryos were then allowed to further develop for 2 h (A) or 12 h (B), at which point they were reacted with DIFO-555 (100 μM, 1 h) and then imaged by confocal microscopy. Shown are maximum intensity z-projection images of superficial enveloping layer cells. Green, DIFO-488; red, DIFO-555. (Scale bar: 10 μm.)