The Drop of Water (Story Time, Episode 84)

Of course, you must know what a microscope is, that round magnifying glass which makes everything look hundreds of times larger than it really is. If you take it and hold it close to your eye and look at a single drop of ditchwater, you'll see thousands of strange little creatures, such as you couldn't imagine living in a drop of water. But they are really there. They look almost like a plateful of shrimp, all jumping and crowding against each other, and they are so ferocious they tear off each other's arm and legs; yet in their own way they are happy and merry.