NAD+ is a crucial coenzyme found in all living cells, acting as an electron carrier in redox reactions and playing a key role in cellular metabolism. It exists in both oxidized (NAD⁺) and reduced (NADH) forms. Research has focused on NAD⁺ in relation to mitochondrial function, sirtuin activity, and DNA repair mechanisms. In laboratory settings, NAD⁺ is frequently utilized to study energy homeostasis, enzymatic reactions, and age-related cellular pathways.