A secret of PCR’s success is the continuing evolution of the DNA polymerase used to build new DNA strands using a template strand. “Since its invention, improvements in PCR have largely depended on advancements in enzymology,” says Edita Smergeliene, product portfolio manager for gene detection at Thermo Scientific. It’s difficult to imagine the earliest PCR experiments, before temperature cycling was automated by thermal cyclers, and before the discovery of thermostable DNA polymerase. Back then, PCR runs were very hands-on because researchers had to control sample temperatures manually and add fresh DNA polymerase to each cycle. From the original DNA polymerase derived from E. coli, to the more thermostabile yet error-prone DNA polymerase Taq (derived from Thermus aquaticus), to proofreading DNA polymerases that make fewer mistakes, scientists have tweaked PCR enzymes to meet increasingly specific demands (and free up their time).