Here we give some background information about viruses, microscopes and ponds. If you would like some help with the difficult words, you can find our glossary here.
What is a virus?
Viruses are best known as things that make humans ill, from the common cold and winter vomiting bug to serious diseases like ebola. Most viruses do not affect humans at all, but infect in other animals, plants, and bacteria.
Viruses can not grow or reproduce outside of a living cell; they always need a host to provide it with energy and building materials. They are usually made of a nucleic acid molecule in a protein coat, but may have other components such as a tail or a membrane envelope.
It may help to think of a virus as a robot. Robots only do what they are programmed to do. Virus-robots are programmed to multiply - they want to make more robots like themselves. But they need materials to make copies of themselves. So they find a suitable factory, invade it, stop it making whatever it made before, and use it to make robots. The robots coming out of this factory go to find more factories to change into robot-factories.
You can read more about viruses here.