BAK1 (BCL2 antagonist/killer 1) is a core regulator of intrinsic apoptosis that mediates mitochondrial outer membrane permeabilization (MOMP). Upon apoptotic stimuli, BAK1 oligomerizes at the mitochondrial outer membrane to form pores, releasing pro-apoptotic factors including cytochrome c into the cytosol, which activates caspase 9 and downstream effector caspases 1. BAK1 exhibits distinct oligomerization kinetics compared to its partner BAX, organizing into smaller structures with faster assembly rates; however, BAK1 recruits and accelerates BAX assembly into growing apoptotic pores 2. The relative abundance of BAK1 and BAX determines pore growth rates and the kinetics of mitochondrial DNA release, thereby controlling activation of the cGAS/STING inflammatory pathway 2. BAK1-mediated release of mitochondrial RNA into the cytoplasm triggers RIG-I-MAVS-dependent immune responses during DNA damage 3. Functionally, unsaturated lipids in the mitochondrial membrane environment promote BAK1 pore activity 4. Clinically, BAK1 rs210138 polymorphisms show significant association with increased testicular germ cell tumor risk 5, and elevated BAK1 expression in hepatocellular carcinoma renders tumors sensitive to therapeutic targeting while normal hepatocytes remain resistant 6.