FCCP (CAS 370-86-5), chemically known as carbonyl cyanide p-trifluoromethoxyphenylhydrazone, is a lipophilic mitochondrial uncoupler frequently used in cellular biology research. It functions by transporting protons across mitochondrial membranes, dissipating the proton gradient essential for ATP synthesis. FCCP exhibits potent inhibitory activity (IC50 = 0.51 µM in T47D cells), effectively disrupting oxidative phosphorylation. Experimentally, FCCP increases cellular oxygen consumption and suppresses hypoxia-inducible factors (HIF-1α and HIF-2α), reducing downstream gene expression such as VEGF. In rodent embryos, FCCP impairs mitochondrial function, resulting in decreased ATP production, lower birth weight, and altered metabolic phenotypes in offspring, highlighting its utility in studying metabolic regulation and mitochondrial biology.