Tiny Living Helpers: Bugs Too Small to See

There are living things all around you, right now, so small you could fit a million of them on the head of a pin. They are called microbes. Most of them are not scary at all -- some microbes make your bread rise, some make yogurt yummy and tangy, and scientists have even taught tiny microbes to make medicine that helps sick people feel better!

- What a microbe is and why we can't see them with just our eyes - Two jobs that helpful microbes already do for us every day - How scientists can gently change a microbe to give it a brand-new job - Why scientists are careful and follow safety rules when they do this

A microbe is a living thing so tiny you need a special tool called a microscope to see it. Some microbes are called bacteria. They are not bugs like ants or ladybugs -- they are much, much smaller, and they are made of just one single tiny cell. Even though they are too small to see, microbes are alive: they eat, they grow, and they can even make copies of themselves. Microbes live almost everywhere -- in soil, in water, in the air, and even inside your own tummy, where friendly microbes help you digest your food!

Before scientists ever changed a single microbe on purpose, microbes were already hard at work. Yeast is a tiny living microbe that bakers have used for thousands of years -- when you mix yeast into bread dough, the yeast eats the sugar in the dough and lets out tiny bubbles of gas, which is exactly why bread puffs up and gets fluffy in the oven. Another helpful microbe turns milk into yogurt by making it thick and a little bit sour in a yummy way. People have used these helpful microbes for a very, very long time, even before they understood what microbes were!

Scientists have learned how to gently adjust a microbe's tiny inside instructions so it makes something new and helpful. One real example: scientists changed a microbe so that instead of just growing on its own, it makes insulin -- a medicine that people with a disease called diabetes need every single day to stay healthy. Before scientists learned this trick, insulin medicine was very hard to make. Now, tiny changed microbes in big clean factory tanks make insulin for millions of people around the world. Scientists always work very carefully and follow strict safety rules when they do this, testing everything again and again to make sure the new microbe is safe and does exactly the one job it's supposed to do.