No / A novel, green, and continuous method for solid-state polymorphic transformation of artemisinin by high temperature extrusion has recently been demonstrated. This communication describes attempts to understand the mechanisms causing phase transformation during the extrusion process. Polymorphic transformation was investigated using hot stage microscopy and a model shear cell. At high temperature, phase transformation from orthorhombic to the triclinic crystals was observed through a vapor phase. Under mechanical stress, the crystalline structure was disrupted continuously, exposing new surfaces and accelerating the transformation process.