Polymerase Chain Reaction (PCR) turns a tiny bit of DNA into a much larger amount which can subsequently be sequenced.
In 1983, Mullis figured out a way to multiply the tiniest piece of DNA by orders of magnitude, making millions of copies. This is how the smallest bit of DNA, from bacteria, viruses, historical artifacts, or even crime scenes, can be multiplied and analyzed. Mullis won the Nobel Prize in Chemistry in 1993.
PCR and DNA profiling go together like Sherlock Holmes and Watson. Created by Alec Jeffreys, profiling identifies people or animals and their relationship to one another. Mullis shared the 1993 Nobel Prize in Chemistry.
PCR is the impetus for the science fiction book and movie Jurrasic Park. In that book, minuscule amounts of dinosaur DNA create living dinosaurs. Many wrongfully convicted innocent people are free due to PCR/DNA. Furthermore, the technique helped identify countless violent criminals.
Mullis is an eccentric, moving between serious scientific work and unusual ventures. He owns a business selling jewelry containing artificially grown DNA from famous people (ex: Elvis). He also started businesses to help the immune system identify and auto-mutate cells to enable, for example, a universal flu vaccine. Despite his scientific background, he’s both a climate-change denier and also denies the well-proven link between HIV and AIDS.
Cetus paid Mullis a $10,000 bonus for his work and sold the patent to Roche for $300 million. Predictably, much patent litigation ensued which, for the most part, Roche/Cetus won.