I was reading about the origin of the discovery of viruses. Koch's postulates were originally written to be about Bacteria, because viruses hadn't been "discovered" yet. Shortly after the publication of Koch's postulates, they found a "tiny bacteria," smaller than any that had yet been discovered. Then they found it wasn't even a bacteria, it was something entirely different called a virus. And wouldn't you know it, the way it operates completely evades all 4 of Koch's postulates?