Vortex glass transition in superconductor is the transition below which resistance goes to zero, because the vortices get pinned below a characteristic temperature (Tg) at the defects sites present in the superconductor and stops the flux flow. Some of the superconductors show glassy phase of vortices but not all. Although all real superconductors have defect structures so vortex glass transformation should observe in all dirty limit superconductors, but it’s not, why?