A future energy system where the supply of fuels, heat, and electricity is based exclusively on renewable energies relies heavily on technologies capable of converting fuels into electricity and vice versa (power-to-fuel or P2F) with high efficiency. In such a context, reversible solid oxide fuel/electrolysisElectrolysis cells (SOFCs/SOECs) are of urgent interest. The misfit calcium cobaltiteCalcium cobaltite electrode, [Ca2CoO3−δ]0.62[CoO2] (C349), has appeared as an attractive electrode material for solid oxide cell (SOC) applications due to offering a similar thermal expansion coefficient to that of classical electrolytes (e.g., doped ceria or stabilized zirconia), aligned with its good surface exchange kineticsSurface exchange kinetics. The current chapter provides a review of the understanding and optimization of C349-based electrodes, and within this perspective, the oxygen reaction mechanisms are extensively discussed. Different strategies to improve the electrochemical performance are also highlighted, such as doping, the addition of oxide ion conducting phases, interlayers between the electrode and electrolyte, processing methodologies, and the effect of electrode thickness. Its potential application in reversible SOCs in fuel cellFuel cell and electrolysis operation modes is presented and discussed. Finally, comparison with other Co-based electrodes is performed.