Every living cell relies on the molecule NAD⁺ to keep itself running. Low levels of NAD⁺ have been linked to both aging and a wide range of diseases, including type-2 diabetes, Alzheimer’s, and cancer. Using sophisticated tools that can track the molecule’s metabolic origin and fate, Melanie McReynolds aims to figure out how NAD⁺ is produced and used up. Uncovering what governs NAD⁺ metabolic flux inside cells may clarify – and eventually counter – diseases and aging.