Redox metabolism plays a central role in maintaining homeostasis in living organisms. The electron transfer system in mitochondria produces ATP via endogenous redox molecules such as flavin mononucleotide (FMN), flavin adenine dinucleotide (FAD), and coenzyme Q10 (CoQ10), which have flavin or quinone moieties. One-electron transfer reactions convert FMN, FAD, and CoQ10 to the free radical intermediates FMNH and FADH, and CoQ10H, respectively. Dynamic nuclear polarization-magnetic resonance imaging (DNP-MRI) allows us to visualize free radicals in vitro and in vivo. We present a spectroscopic imaging technology with DNP-MRI, which enables the imaging of multiple free radical intermediates such as FADH and CoQH. DNP-MRI can also identify various endogenous free radical intermediates derived from redox transformations.