Exploiting Defects in a Jam Phase-change materials that can readily switch between crystalline and amorphous states are increasingly finding use in nonvolatile memory devices (see the Perspective by Hewak and Gholipour ). Using high-resolution transmission electron microscopy, Nam et al. (p. 1561 ) show that for Ge ₂ Sb ₂ Te ₅ , the application of an electric field drives crystal dislocations in one direction, leading to their accumulation and eventual jamming, which causes the phase transition. Loke et al. (p. 1566 ) found that by applying a constant low voltage to Ge ₂ Sb ₂ Te ₅ , they could accelerate its phase-switching speeds, without harming the long-term stability of the switched state.