The prefix micro- means extremely small or relating to something tiny. It comes from an ancient Greek word meaning “small,” and when you attach it to the front of another word, it shrinks that thing down to a miniature version.

A microscope lets you see tiny things your eyes normally can't detect, like bacteria or cells. A microwave oven uses very short waves of energy (much shorter than radio waves) to heat your food. Microorganisms are living things so small you need a microscope to see them. When scientists study something at the microscopic level, they're examining details invisible to the naked eye.

The prefix also describes things that are small-scale versions of bigger concepts. A microclimate is the weather pattern in a tiny area, like how it might be cooler and shadier under a large tree than in the sunny yard around it. In the 1970s and 80s, personal computers were called microcomputers because they were much smaller than the room-sized computers that came before them.

Sometimes micro- just means “one millionth,” a precise measurement used in science. A micrometer is one millionth of a meter, and a microsecond is one millionth of a second (incredibly fast, only enough time for light to travel about 300 kilometers).