Meet Megavirus chilensis, a virus so big that it's actually larger than some bacteria:
The particle measures about 0.7 micrometres (thousandths of a millimetre) in diameter.
"It is bigger than some bacteria," explained Prof Jean-Michel Claverie, from Aix-Marseille University, Marseille, France.
"You don't need an electron microscope to see it; you can see it with an ordinary light microscope," he told BBC News.
In the lab experiments conducted by Professor Claverie and colleagues, in which they infected fresh-water amoebas, Megavirus was seen to construct large trojan organelles - the "cells within cells" that would produce new viruses to infect other amoebas.