What is the length in science?

some basic units of length that scientists use to study cells, organelles, or microorganisms follow the rules of the metric system. starting at the length of 1/10 of a centimeter is a millimeter (mm), which is slightly large to be used as this type of measurement, but is still occasionally used. 1/10 of a millimeter is a micrometer (µm), which is a good measurement to use for cells or microorganisms. 1/10 of a micrometer is a nanometer (nm), which is an okay size to measure organelles with. Smaller than a nanometer, scientists rarely use the metric system, which has become to large for purposes, and begin to use relative measurements of which I am not familiar.