Behold, the origin story of every mitochondrion in your cells! The endosymbiotic hypothesis in its most elegant form: "Hey random archaeon, wanna adopt this angry bacterial child that produces energy?" "Sure, what could possibly go wrong?" Fast forward 1.5 billion years and here we are - complex multicellular organisms whose cells are basically just ancient archaeal parents still dealing with their moody bacterial roommates. Evolution's most successful shotgun wedding, and we're the weird descendants.