<p>In this podcast we are going to look at what viruses are. &nbsp;Viruses are a type of microorganism. They are too small to be seen with the naked eye: much smaller than bacteria, and about 100 times smaller than human cells. They come in many different shapes and are present wherever there are cells to infect. In fact, viruses are the most common biological unit on Earth, outnumbering all other types combined!</p>