How many living things fit inside a single drop of pond water? You collect water from a lake or pond and examine it under a microscope. What looks like plain water turns out to be full of tiny organisms. You prepare a wet mount slide and scan it under low power first. When you spot something, you switch to high power for a closer look. You draw each organism and calculate the magnification. Using a key of freshwater microorganisms, you identify and classify what you find. Some are single-celled protists (tiny organisms with a nucleus). Others are multi-cellular. The diversity in one drop of water reveals how complex a pond ecosystem really is.