The study investigates the growth dynamics of conducting filaments in nanoscale resistive switching devices, also known as memristors, which are of significant interest for memory, logic, and neuromorphic applications. Through systematic transmission electron microscopy (TEM) studies, the researchers found that filament growth is primarily driven by cation transport in the dielectric film. Two distinct growth modes were observed: one where the filament starts from the active electrode and grows towards the inert electrode, and another where the filament grows from the inert electrode towards the active electrode. The narrowest region of the filament was consistently found near the dielectric/inert-electrode interface, suggesting this region's critical role in device optimization. The findings provide new insights into the filament formation and dynamics, which can be crucial for improving the performance and reliability of resistive memory devices.The study investigates the growth dynamics of conducting filaments in nanoscale resistive switching devices, also known as memristors, which are of significant interest for memory, logic, and neuromorphic applications. Through systematic transmission electron microscopy (TEM) studies, the researchers found that filament growth is primarily driven by cation transport in the dielectric film. Two distinct growth modes were observed: one where the filament starts from the active electrode and grows towards the inert electrode, and another where the filament grows from the inert electrode towards the active electrode. The narrowest region of the filament was consistently found near the dielectric/inert-electrode interface, suggesting this region's critical role in device optimization. The findings provide new insights into the filament formation and dynamics, which can be crucial for improving the performance and reliability of resistive memory devices.