In article number 1704123, Yung-Eun Sung and co-workers discuss the design of nanoscale electrocatalysts for energy conversion and storage devices is discussed in terms of the nanoparticle degradation mechanism under electrochemical operating conditions. Based on the fundamental understanding, the importance of the functional relationship between the activity and the stability of nanoparticles is considered and five distinctive strategies to bridge the gap in the functional relationship for achieving superior properties in electrochemical energy applications are discussed.