I had been impressed by the fact that biological systems were based on molecular machines and that we were learning to design and build these sorts of things.

The other advantage is that in conventional manufacturing processes, it takes a long time for a factory to produce an amount of product equal to its own weight. With molecular machines, the time required would be something more like a minute.

Protein engineering is a technology of molecular machines – of molecular machines that are part of replicators – and so it comes from an area that already raises some of the issues that nanotechnology will raise.