A retrovirus is a type of virus that, as part of its life cycle, creates a piece of DNA that is incorporated into the DNA of the host cell, which then creates the RNA and proteins that allow the retrovirus to make copies of itself. Other types of virus merely use their own RNA to hijack the cell to create the RNA and proteins without creating DNA in the process. Two well known retroviruses are HIV and hepatitis B. Some rare types of retroviruses can even use the host to make copies of itself when the host reproduces, passing the virus on to the following generation.