What are Micro-Organisms? Micro-Organisms are tiny living creatures. They are so small that you need a microscope to see them. Micro-Organisms are all around us in the air and in water. Some micro-organisims are harmful to us, whereas others are helpful to us. Three types of micro-organisims are - Virus Bacteria Fungi Viruses are small micro-organisims that can cause sicknesses such as colds. If you catch a virus the best thing to do is let your body fight it on its own. If you catch a virus it can also cause temperatures as this is your body's way of fighting the virus. Bacteria are small living things found everywhere. They are too small to be seen without a microscope. Some bacteria is good and some is bad. Bad bacteria can make you sick whereas the good bacteria helps you when you are sick. Fungi is a group of micro-organisims that include moulds and yeasts, and also mushrooms. Yeast helps with bread-making. Mould grows on foods if they are not stored properly. It also can grow on walls. Mould makes you sick. Some micro-organisims are harmful, so its important to know how to avoid spreading the bad ones.