Spin Transfer Torque Magnetic Random Access Memory (STT-MRAM) is a type of emerging memory which holds the promise of high speed, high endurance, non-volatility, and good scalability. Since the theoretical prediction of the STT switching mechanism in 1996, significant progress has been made in the field, largely through materials innovations. In this talk, I will review the key materials discoveries that enabled the advancement of STT-MRAM technology. This includes the theoretical prediction and experimental realization of large tunneling magneto-resistance (TMR) with MgO tunnel barrier and the discovery of CoFeB based materials with interfacial perpendicular magnetic anisotropy (iPMA). I will also discuss the critical materials parameters impacting STT-MRAM device switching performance, for example, the Gilbert damping constant and exchange stiffness of the free layer material.