Armed with the table above, and all the prefixes and symbols, it is possible to measure almost anything that has physical dimensions.|
One meter (m) is slightly longer than the American yard, and a centimeter (cm) is slightly less than half and inch. These are using of measure humans would use in their everyday lives, measuring distances to work, or dimensions of a book or table.
A millimeter (mm) is about is about the thickness of a pencil line, and is useful in science and engineering to ensure a close fit between parts, or make certain small dimensions more accurate.
A micrometer (µm) is at the limit of human vision and is about the thickness of a very thin piece of paper. These units would not be used in everyday human life, but in an engineering or scientific laboratory.
Below the micrometer, things get very small. A nanometer (nm) is only used in scientific laboratories and in this range of size a large, globular protein would be about 3 to 6 nm across.