**4. Metrology for other biologicals**

There are several other important categories of biological materials other than nucleic acids and proteins. They include cells, microorganisms and glycans. One may want to extend the scope to include lipids. Small molecules are also play important roles in biological processes as nutrients or metabolites, but it will be better to categorize them as chemicals instead of biologicals. In technical prospects, biologicals here are classified as large molecules that are not readily quantifiable by chemical analysis.
