Way back in 1674, a frog helped Antoni van Leeuwenhoek make an incredible discovery. Antoni was an amateur scientist from Holland, so fascinated by microscopes ____ he'd built some of his own. One rainy day, as he went for a walk, a leaping frog ____(draw) his attention to a puddle.

    Antoni collected a drop of puddle water and put it____ his microscope. He was amazed____ (see) a whole community of creatures swimming in this one drop — tiny beings no one had ever seen before.

    These tiny beings, called microbes, are everywhere: in dirt, in food and on your kitchen table. People ____ (cover) in them, too.____ you were to count all the microbes on and inside your body, you would find your body has more microbes than the world has people — over 6 billion!

    Microbes can't survive on ____(they) own. They need food. After ____(settle) into a home — you, for instance — they steal vitamins and other nutrients and leave behind dead cells and poisonous liquids called toxins. Some microbes can make you sick. People usually call these ones germs____ (lucky) for you, there are more ____ (help) microbes, working together to keep you healthy, than bad ones.