1961 was of course a very exciting year. During that year we published two papers. One was on the messenger RNA experiments, and the other was on the general nature of the genetic code. Of course, that was incredibly exciting, but there was still a lot more work to do in order to follow these things up. But already I think in 1962, my interests were already turning to different matters. And during that year Francis Crick and I began a long series of conversations, which we continued over several years, which is: what should we do next? It seemed, as it does happen in all science, that when one gets to this stage there seem to be only what the military people call mopping up operations. And of course such was the thrill of doing molecular biology that one didn't want to be involved in that, and one would rather go forward to fresh pastures. I had during 1961, had a number of discussions with François Jacob – who was… who did the messenger RNA experiments with me – about DNA replication. And we did some experiments together in early 1962 which tried to test the model that we proposed. This was called the replicon. In those days everybody defined a unit in the same way physicists defined units, and the first person to do that was Seymour Benzer. Seymour Benzer defined three units: the cistron, which was the unit of complementation; the muton, which was the unit of mutation; and the recon, which was the unit of recombination. And of course only one of those has survived, the cistron, and the reason the other two didn't survive was that one should always see what one's units sound like in a different language. And since we had numerous French colleagues, the other two didn't survive because one sounded like a sheep, and the other one sounded like the things Paris taxi drivers call each other. So those two got eliminated. Some… a short while thereafter, and I think it was 1957 or 1958, I invented the word codon, which was… which has also survived. And that was a word to describe the… the units that would be… would be… specify the amino acids, which of course we used that because we didn't know at the time that they were triplets. We thought they might be. And so in due course we had the operon which is… Jacob and Monod used for the… for the unit of genetic expression in bacteria. That is the unit that was regulated, and that survived, in fact one often thought of giving lectures entitled “A Night at the Operon”. And the word that François and I invented for the unit of replication was of course the replicon, and the replicon has survived as well.