All around the world -- in the sea, in the soil, in the air, and in your body -- there are living things so tiny that millions could fit on an ant's antenna. They're busy doing all sorts of things, from giving you a cold and making yogurt to eroding mountains and helping to make the air we breathe. If you could see them with your eye, you'd find that they all look different, and that they're really good at changing things into something else and at making many more microbes like themselves! From Nicola Davies comes a first exploration for young readers of the world's tiniest living organisms.