Watching a phase transition unfold

Ultrafast Microscopy The layered material 1 T -polytype of tantalum disulfide has several intricate charge-ordered phases. How exactly one phase transitions into another is tricky to observe directly with current technologies. Danz et al. used pump-probe ultrafast dark-field electron microscopy to follow such a transition with fine spatial and temporal resolution (see the Perspective by Kogar). To achieve that goal, they shaped the electron beam used as the probe to bring out the features peculiar to the transition. Science , this issue p. [371][1]; see also p. [341][2] [1]: /lookup/doi/10.1126/science.abd2774 [2]: /lookup/doi/10.1126/science.abf1406