So that we now have the technology for subculturing cells for long periods of time, freezing them or preserving them, so that they can be resurrected at a much later date.  That was about the state of the technology at the time that I am now discussing. In addition to which I have already mentioned, but will re-emphasis the observation that rarely, with human cells in culture from normal tissues, will a transformation occur that means that the normal cells that you've cultured now show cancer cell properties, namely the ability to undergo unlimited cell cultivations, to have the appearance or the cytology of cancer cells, to have biochemical properties of cancer cells, etc. So this phenomenon is very important. It was recognised at that time as being important. Why? Because if you could understand how a normal cell suddenly transformed into a cancer cell, you would have a new approach to doing research on cancer biology. You wouldn't have to use whole animals, certainly not humans, but you now had the possibility of investigating cancer at the cellular level in bottles, which allowed for all kinds of experiments. So that concept has to be understood in respect to the importance of what we call transformation.