Tips of MTs growing in vitro. (A–C) (Left) Slices through cryo-tomograms of MT ends (grayscale images) and (right) models drawn on protofilaments seen in slices at different orientations around the MT axis. Bar = 50 nm. (D) Curves representing the shapes of many protofilaments. (E and F) Distribution of their lengths and (F) distribution of their curvatures. (G) Average curvature in degrees/dimer of many protofilaments as a function of distance from the protofilament’s tip. From Mcintosh et al. (2018).