Hydrogen is a possible candidate for replacing oil in the long-term in many applications such as transportation.Storage of hydrogen at near ambient temperatures and pressures is a puzzling issue for the scientific community.Hydride storage is one of the most promising, safe solutions for sustainable use. The magnesium and its alloys have attracted a lot of attention since the gravimetric hydrogen capacity is relatively important (7.6 wt. %) and the systems are reversible. The Mg-based hydrides compounds have high enthalpy of formation making them too stable for practical applications. Additionally they have some kinetics limitations that can be partially overcome by catalysts or nanostructuring of the alloys. Apart from these, another approach to lower the reaction enthalpy of MgH2 is composite preparation with the hydrogen storage materials. The present book is an outcome of the research on the destabilization of MgH2 by composite formation with hydrogen absorbing ZrCr2 alloy.