So let's suppose this is the nucleus of our mouse cell. We can hold the nucleus on one end with some type of instrument, for example a larger pipet, we can hold this in place while at the other end we poke with a special type of micropipet that contains that DNA fragment that we want to inject. And so by injecting this nucleus of the cell can essentially accept and incorporate that DNA molecule into its genome. And in the lab about 2% of the mouse cells that essentially are injected with this method will incorporate this DNA molecule into their cell genome. Now let's move on to method number two injection with viral agents. And the viral agents that are very effective are retroviruses.