Nanobacteria is the name of a possible class of living organisms; specifically cell-walle microorganisms with a size much smaller than the generally accepted lower limits for life, about 200 nanometres for bacteria. 200 nm happens to be the size of the smallest object which could be resolved in a standard light microscope. In 1996, the size was supposedly derived from the smallest volume required by known organisms, where nanobacteria were unknown.