Non-destructive Nuclear Magnetic Resonance (NMR) plays a crucial role to unveil mechanisms of batteries under operation conditions. In situ NMR characterization offers intermediate information, which is very important for the performance of working devices, such as diffusion, kinetics, and dynamics that cannot be obtained by conventionalex situ approaches. This chapter introduces general considerations for performing in situ NMR experiments and summarizes designs of battery cells used for in situ NMR characterization. In addition, Magnetic Resonance Imaging (MRI) is a powerful method for visualization of materials with the aid of a magnetic field gradient to encode positions of nuclear spins. In situ MRI studies have contributed to an understanding of the fundamental phenomena that are associated with a battery's performance and failure mechanisms. Here we provide an overview of "electrochemical MRI"developments over the past two decades.