This study investigates the microscopic mechanisms and kinetic pathways of amorphous-amorphous transitions (AAT) in silicon under rapid pressure changes using advanced machine-learning potential and local structural analysis. The researchers identify three distinct amorphous forms—low-density amorphous (LDA), high-density amorphous (HDA), and very-high-density amorphous (VHDA)—and two crystalline forms—β-Sn and simple hexagonal (sh). They find that the transition from LDA to HDA occurs through nucleation and growth, resulting in non-spherical interfaces, while the reverse transition occurs through spinodal decomposition. Further pressurization transforms LDA into VHDA, with HDA serving as an intermediate state. The final amorphous states are inherently unstable and transition into crystals. The findings highlight that AAT and crystallization are driven by joint thermodynamic and mechanical instabilities, assisted by preordering, without diffusion. This research provides insights into the unique mechanical and diffusion-less nature of AAT, distinguishing it from liquid-liquid transitions. The study also emphasizes the importance of preordering in AAT and crystallization, offering valuable insights into the fundamental principles governing structural transformations in various materials.This study investigates the microscopic mechanisms and kinetic pathways of amorphous-amorphous transitions (AAT) in silicon under rapid pressure changes using advanced machine-learning potential and local structural analysis. The researchers identify three distinct amorphous forms—low-density amorphous (LDA), high-density amorphous (HDA), and very-high-density amorphous (VHDA)—and two crystalline forms—β-Sn and simple hexagonal (sh). They find that the transition from LDA to HDA occurs through nucleation and growth, resulting in non-spherical interfaces, while the reverse transition occurs through spinodal decomposition. Further pressurization transforms LDA into VHDA, with HDA serving as an intermediate state. The final amorphous states are inherently unstable and transition into crystals. The findings highlight that AAT and crystallization are driven by joint thermodynamic and mechanical instabilities, assisted by preordering, without diffusion. This research provides insights into the unique mechanical and diffusion-less nature of AAT, distinguishing it from liquid-liquid transitions. The study also emphasizes the importance of preordering in AAT and crystallization, offering valuable insights into the fundamental principles governing structural transformations in various materials.