In 1983, Mullis was working for Cetus Corp. as a chemist. That spring, according to Mullis, he was driving his vehicle late one night, when he had the idea to use a pair of primers to bracket the desired DNA sequence and to copy it using DNA polymerase. This would allow a small strand of DNA to be copied almost an infinite number of times. Cetus took Mullis off his usual projects to concentrate on PCR full-time. Mullis succeeded in demonstrating PCR on December 16, 1983.