Pre- (a) and post-expansion (b) images of a dividing PtK1 cell immunostained for tubulin (green) and the kinetochore protein HEC1 (red). Scale bar, 5 μm. c, d Magnified views of microtubule-kinetochore attachments from the boxed regions in a and b. Scale bars, 500 nm. e, f End-on views of the boxed regions in a and b. Scale bars, 2 μm.