Once in the cell, the capsid protective sheath will be dissolved, liberating the viral RNA and the reverse transcriptase. Now, in order to effectively infect the cell, the viral RNA needs to travel into the cell's nucleus (where it can change the T-cell's rules and convert it into a virus factory). However, for that to happen, an important transformation needs to take place.

Normally, the T-cell's nucleus communicates with the rest of the cell by transforming DNA into RNA and sending it out of the nucleus. (In all the cells of our body, RNA acts as a messenger between the nucleus and the rest of the cell. The DNA makes RNA and sends it out to convey orders.) The genetic material's passport to leave the nucleus is to be transformed into a single-stranded RNA. In the same fashion, the passport to enter the nucleus is to be transformed into double-stranded DNA.

Viral RNA needs to become DNA in order to reach its final destiny. Reverse transcriptase allows the RNA to borrow material from the cell and to "write backwards" a chain of viral DNA

HIV is a retrovirus because of its capacity to transform RNA into DNA, reversing the natural process that takes place in cells. This is accomplished by a substance called reverse transcriptase. Retroviruses are a special family of viruses to which only a few known viruses belong (although many others might yet be discovered).