CFU is colony forming unit. CFU is colony forming unit, colony forming unit refers to the total number of colonies of microorganisms such as bacteria, molds, yeasts, etc. per unit volume. When counting live bacteria in culture, the colony formed by the growth and reproduction of a single bacterium or multiple bacteria aggregated into a cluster on solid medium is called colony forming unit to express the number of live bacteria. The measurement of colony forming unit is different from the general counting method, usually directly under the microscope to count the number of bacteria will count all the live and dead bacteria, but CFU only counts the live bacteria. Colony forming unit is commonly used CFU method, that is, plate counting method, plate counting method is part of the sample out of the mix, with the appropriate dilution solution for gradient dilution, take a certain amount of dilution solution coated or dumped agar plate, incubated at a suitable temperature for a certain period of time, and then through the naked eye observation or electronic counters for all the visible colonies to be counted. Theoretically, each colony consists of a single cell reproduction, the number of colonies is traditionally called a, but a colony is not necessarily a microorganism generated, but may also be generated by a cluster of microorganisms (a bacterial group), so it is not accurate to call a, the accurate call is the colony-forming unit, cfu / g refers to the total number of microbial colonies per gram of the sample contains.