So in step number one, we basically have the HIV, the virus that approaches the cell membrane of our human cell. And in step two we have the binding process taking place. These purple protrusions basically bind to the receptors, the protein receptors found on the cell membrane and specifically they bind to the protein receptors called CD four and CCR four. Now, once that binding takes place and the HIV recognizes this specific type of human cell, we have the fusion taking place, the fusion between this lipid rich layer found on the virus and the cell membrane of that human host cell. So in three, once bound, the lipid rich envelope of the virus fuses with the plasma membrane of the host human cell injecting the contents, including the proteins as well as the single RNA molecules into the cytoplasm of that cell. And next we move on to step number four.