The electrochemical flow capacitor (EFC) described by E. C. Kumbur, Y. Gogotsi, and co-workers utilizes a flowable slurry of capacitive carbon particles in an aqueous or organic electrolyte. The proposed concept combines the scalability of flow batteries with the high power density and long lifetime of electrochemical capacitors. EFC technology also decouples energy and power ratings, which is important for storage and use of energy from highly fluctuating sources. The proof-of-concept study on page 895 presents promising initial performance data and discusses further development steps for this technology. Flow cell design by the Materials Research Center (Ukraine) and cover design by Kristy Jost (USA).