How Small Are Viruses?

How small are viruses 

Well, it's a great question of asking how small viruses are. Well, viruses are so small that some of them can even enter a bacterium and infect it. In fact, viruses are typically 1000 times smaller than a bacterium. They are between 17 to 300 nanometers long, one nanometer being one billionth of a millimeter. As you may have guessed, they can not be seen with an ordinary microscope; you will have to use a special electron microscope to view a virus.