Metal and nitrogen-doped carbons (M-N-Cs) are a widely studied class of materials due to the atomically dispersed, nitrogen-coordinated MNx sites that are hypothesized to be catalytic active sites for a variety of chemical reactions. In particular, Ni-N-C catalysts show high selectivity for CO under electrochemical CO2 reduction conditions and Fe-N-C catalysts have been investigated for their activity (ORR) in both acidic and alkaline environments. There has been considerable research interest in identifying the exact structure of the catalytic active site in M-N-Cs to facilitate the design of optimized, next-generation M-N-C catalysts. However, the presumed active MNx sites are challenging to characterize due to their lack of long-range order which prevents the use of diffraction-based techniques and because of the wide CO2R active sites, however, none of the characterization techniques employed have been able to ascertain the specific geometry and coordination of the active site. At the current state of knowledge, the existence of atomically dispersed, nitrogen-coordinated Ni sites has been clearly indicated but further investigation is needed to precisely define the site structure in these materials.