微生物是很小很小的生物，我们的眼睛看不到，要用显微镜才能看清楚。

Microorganisms are very, very small living things that our eyes cannot see; you need a microscope to see them clearly.

细菌和病毒都是微生物，有的对人有害，有的却很有用。

Bacteria and viruses are both microorganisms; some are harmful to humans, while others are very useful.