In most cases, the current flows uniformly through the device in the HRS and is restricted to a local region with high conductance known as a conducting filament (CF) in the LRS. [3] Among them, a specific memory device is termed as conductivebridge RRAM (CBRAM), where the formation/rupture of metallic conductive filaments are dominated by cation migration and redox processes. [4] Meanwhile, volatile resistance switching behaviors are commonly observed in CBRAM as threshold switching (TS). Analogous to the nonvolatile electrochemical metallization mechanism in terms of materials and structures, [5] the electrical resistance of such a threshold switching memristor (TSM) could decrease by orders of magnitude when an electric field is applied due to the formation of CFs with active metal (such as Ag or Cu) atoms. [6] Differently, the resistance returns back spontaneously after the termination of the external bias, yielding a superior I-V nonlinearity and unique temporal conductance evolution dynamics. [7] Recent years, the threshold switching memristors based on active metals are also called "diffusive memristors" to emphasize the diffusion dynamics of the metal species. [8] To be more comprehensively, redox-diffusive threshold switching memristor (RDTSM) might be the best choice to demonstrate the overall switching behavior. [1a] RDTSM has gained significant attention due to its similar advantages to RRAM, such as the simple structure, great fabricability and integrability, and compatibility with conventional CMOS technology. More importantly, it has great potential in many vital applications, such as two-terminal selectors with high nonlinearity, [9] high-powerefficient synaptic or neuronal devices with novel functions. [8,10] A specific application requires a correspondingly proper device. Figure 1 displays the measurement schematic of the key parameters of RDTSM, including selectivity (or nonlinearity), compliance currents, switching voltages (including threshold voltages and hold voltages),TS mode (unidirectional and bidirectional, as shown in Figure 1a,b, respectively), switching slopes (Figure 1c), response time (including delay and relaxation, as shown in Figure 1d) and endurance, which are all up to the material composition and device structure. [11] Therefore, With the rapid development of information technique in the big-data era, there is an extremely urgent demand for new circuit building blocks, represented by resistive switching memristors with high speed, high-density integration, and power-efficiency, to overcome the limitations of electronic device scaling and thus achieve non-von-Neumann neuromorphic computing. Redox-diffusive threshold switching memristors, based on the volatile formation/rupture of metallic conductive filaments, are attracting great attention for many novel applications, ranging from selectors to synaptic and neuronal devices. Here, how to design a proper redox-diffusive threshold switching memristor is comprehensively introduced, with particular focus on the effect of the devic...