Rompolas et al. describe a new, non-invasive intravital two-photon imaging approach for visualizing cells over long periods of time. The authors used this method to study the physiological regeneration of hair follicles in live mice. They visualized entire hair follicles and monitored skin epithelial stem cells and their progeny through the specific expression of a histone H2B–GFP fusion protein, which provides a strong nuclear signal that can resolve individual cells. Consistent with earlier studies, stem cells were quiescent during the initial stages of hair regeneration, whereas their progeny proliferated more actively. They also observed that follicles could rapidly stretch downwards and that, at advanced growth stages, cells of the lower hair follicle were capable of long-range migration. Thus, this method revealed previously unappreciated dynamic cellular behaviours. Last, laser ablation experiments enabled them to demonstrate that the mesenchyme is required for hair growth initiation, reiterating the importance of epithelial–mesenchymal crosstalk.