Currently, there is an urgent global need for electrochemical energy storage materials that simultaneously provide high power and high energy density. One strategy to achieve this is to use reversible surface or near-surface Faradaic reactions to store charge in pseudocapacitive materials. This enables the material to surpass the capacity limitations of electric double-layer capacitors and the mass transfer limitations of batteries. The research conducted along this path over the past decade has tremendously increased our understanding of pseudocapacitance and the materials that exhibit this phenomenon. In this chapter, an extensive introduction is provided for newly developed pseudocapacitive materials.