Biofilms form in aquatic systems on nearly all surfaces and thus represent a part of the microbial community. Three dimensional structures develop from bacteria cells extracellular polymer materials and particles. The colonization of a surface does not take place evenly but rather in a non-uniform manner. When electromagnetic waves with a wavelength of several hundredths of a nanometer hit a biofilm they can be reflected strewn or absorbed. An exact determination of the population density can be achieved by measuring a surface larger than one cubic centimeter.
The colonization density can be determined accurately by measurin a surface that is larger than one square centimetre.