Dynamic MTs grow along MTs and are bundled. EB3-GFP and mCherry-tubulin were coexpressed and simultaneously imaged in plated fibers (A1; Video 4). EB3-GFP (green) moves along static mCherry-tubulin tracks (red; A2 kymograph). The asterisk indicates a nucleation spot and the arrows point to EB3-GFP–labeled MTs growing toward each other. G-STED superresolution microscopy of FDB fibers stained for α-tubulin resolves MTs into two or more components (B and C; panels with blue arrowheads show confocal images; panels with red arrowheads show the corresponding G-STED image at a resolution of 65 nm). A black arrowhead points to a probably unresolved MT. Bars: (A) 10 µm; (B and C) 2.5 µm; (A2, vertical time axis) 60 s.