Epithelial trail cells collectively migrate in MES removal. Confocal live imaging of GFP expression in E15.5 CrectTg/0; R26nTnG/+ secondary palate sagittal section shows a trail being incorporated into the oral epithelium (bottom of image). Bright GFP signal remaining in area adjacent to trail are likely apoptotic debris unconnected to trail cells. Animation on the right shows cell-tracks overlaid on the confocal imaging. Each tracked cell is represented by a colored sphere and respective time-coded tail. Images were captured every 15 minutes for 18 hours. Scale bar, 10μm.