(A) Kymographs of representative time-lapse imaging series of mitochondria (mtYFP, 0.9 fps, A) at P9 (left), P15 (middle), and P21 (right). Top panels show still frames at t = 0s of the branch segments depicted in the kymographs in the bottom panels. (B) Summary data of the motile fraction of mitochondria across development (P9 n = 10 RGCs, P15 n = 9 RGCs, P21 n = 7 RGCs). (C, D) Analogous to A (C) and B (D) but for time-lapse imaging of peroxisomes labeled with SKL-GFP (P9 n = 11 RGCs, P15 n = 10 RGCs, P21 n = 12 RGCs). (E–G) Bars (error bars) indicating the mean (± SEM) duration of uninterrupted runs (E), duration of pauses (F), and speed during uninterrupted motion (G) for mitochondria at P9 and P15 (P9 n = 65 mitochondria, P15 n = 32 mitochondria). See also Video 1. mtYFP, mitochondrially targeted yellow fluorescent protein; RGCs, retinal ganglion cells.