In 1965, a husband-and-wife team of biologists named Thomas and Louise Brock, while on a summer study trip, had done a crazy thing. They had scooped up some of the yellowy-brown scum that rimmed the pool and examined it for life. To their, and eventually the wider world's, deep surprise, it was full of living microbes. They had found the world's first extremophiles—organisms that could live in water that had previously been assumed to be much too hot or acid or choked with sulfur to bear life. Emerald Pool, remarkably, was all these things, yet at least two types of living things, Sulpholobus acidocaldarius and Thermophilus aquaticus as they became known, found it congenial. It had always been supposed that nothing could survive above temperatures of 50 degrees centigrade (122 degrees Fahrenheit), but here were organisms basking in rank, acidic waters nearly twice that hot.

For almost twenty years, one of the Brocks' two new bacteria, Thermophilus aquaticus, remained a laboratory curiosity until a scientist in California named Kary B. Mullis realized that heat-resistant enzymes within it could be used to create a bit of chemical wizardry known as a polymerase chain reaction, which allows scientists to generate lots of DNA from very small amounts—as little as a single molecule in ideal conditions.