Overcoming the strength-ductility trade-off has motivated tremendous efforts to develop advanced metallic materials including high entropy alloys. Recent studies show that both strength and ductility of bainitic steels are significantly increased during tensile tests at -196 ℃ compared to room temperature [1]. To understand the observed counterintuitive plasticity and fracture phenomena in BCC steels, systematic investigations on the cryogenic plasticity and damage in bainitic and martensitic steels have been conducted by integrating continuum damage mechanics and micromechanical approaches. Tensile tests using various specimen geometries have been performed at different cryogenic temperatures. Continuum damage mechanics based finite element simulations have been performed to extract the critical strain and stress values under various loading conditions. On the microscopic scale, the phenomenological crystal plasticity model combined with representative volume element has been used to simulate the evolution of microstructure under the influence of temperature and stress state. A coupling scheme is implemented to bridge the deformation behaviour at two scales [2]. The results indicate that the stress triaxiality is a dominant factor which governs the existence of cryogenic plasticity in the investigated BCC steels with relatively fine hierarchical microstructure features.