Metal-assisted chemical etching (MacEtch) is an unorthodox anisotropic etching method, that defies the isotropic nature of wet etch through local electrochemical effect. In this talk, I will discuss the history, mechanism, and its applicability at the device level to Si, Ge, GaAs, InP, InGaAs, and wide bandgap semiconductors including beta-Ga₂O₃. In particular, forward MacEtch, where etching takes place directly underneath the metal catalyst patterns, produces site-controlled semiconductor nanostructures with unpresented aspect ratio (> 100:1). Inverse-MacEtch (I-MacEtch), bypassing the metal edge roughness, allows the formation of atomically smooth and damage-free sidewalls. Magnetic-field guided MacEtch (h-MacEtch) enables 3D control of the etching trajectory. Self-anchored catalyst (SAC)-MacEtch, using porous catalyst patterns, leads to the fabrication of vertical vias by preventing the catalyst from detouring. This etching method could have profound impact on a wide range of semiconductor fabrication processes, because of its simplicity, versatility, and the absence of high energy ion-induced damage.