Upon initiation of apoptosis BAK and BAX oligomerise on the mitochondrial outer membrane, disrupting the membrane bilayer and forming pores. This process releases cytochrome c - a crucial juncture that commits the cell to death. Structures of BAK oligomers remain elusive however a body of evidence supports dimers as a core unit within the oligomeric structures. This talk will discuss our recent structures of BAK dimers that have been obtained for the first time by activating monomeric BAK. These activated BAK dimers are functional and provide direct evidence for the conformational changes required for BAK to disrupt membranes and form pores. They are also the smallest functional unit for recombinant BAK or BAX described so far. The structure corroborates new ideas on how BAK interacts with lipids to disrupt membranes providing new insights into the enigmatic apoptotic pore.