Many correlated systems feature an insulator-to-metal transition that can be triggered by an electric field. Although it is known that metallization takes place through filament formation, the details of how this process initiates and evolves remain elusive. We use in-operando optical reflectivity to capture the growth dynamics of the metallic phase with space and time resolution. We demonstrate that filament formation is triggered by nucleation at hotspots, with a subsequent expansion over several decades in time. By comparing three case studies (VO₂, V₃O₅, and V₂O₃), we identify the resistivity change across the transition as the crucial parameter governing this process. Our results provide a spatiotemporal characterization of volatile resistive switching in Mott insulators, which is important for emerging technologies, such as optoelectronics and neuromorphic computing.

许多相关系统具有可由电场触发的绝缘体到金属的转变。尽管已知金属化是通过细丝形成发生的，但该过程如何启动和演变的细节仍然难以捉摸。我们使用操作中的光学反射率来捕捉具有空间和时间分辨率的金属相的生长动态。我们证明细丝形成是由热点处的成核触发的，随后在几十年的时间里膨胀。通过比较三个案例研究（VO ₂、V ₃ O ₅和 V ₂ O ₃)，我们将过渡过程中的电阻率变化确定为控制该过程的关键参数。我们的结果提供了莫特绝缘体中易失性电阻转换的时空表征，这对新兴技术（如光电子学和神经形态计算）很重要。