It isn't technically necessary; it is used for convenience, to avoid using very small or very large numbers.
Multiple and sub-multiples are used when the range of values is too large to be measured in a single unit.
these are used to express very large number small and very small
large surface area
A bushbaby is a small primate with very large eyes that lives in sub-Saharan Africa.
A ribosome is made of two parts: an large protein sub unit and a smaller rRNA sub unit. Proteins are strings of amino acids whereas RNA is a string of ribose-based nucleotides.
Sub-unit C
Sugars
Amino acids
Nucleotides
large to small: section subsection sub-heading category 04/07/2014
nucleotides