Lithium metal anode is critical for new generation of high energy batteries. We identified that the two root causes of Li metal problems are high chemical reactivity and infinite relative volume change during Li metal plating and stripping. Nanoscale materials design represents a new powerful paradigm shift and offers new solutions to address these challenges. Here I will present our understanding and progress on: 1) Nanoscale design of host and interface for Li metal anodes; examples of host materials include graphene oxides, hollow carbon spheres, metal fluoride and oxide. We also developed robust interfacial layer materials and synthesis process for BN, Li₃N and LiF. 2) Demonstration of cryogenic electron microscopy applied to battery materials research, leading atomic scale resolution of Li metal dendrite and solid electrolyte interphase. We also established the correlation of the SEI structure with battery performance.