size comparison of microorganisms Meters Visibility scale Relative size of Microbes 10-3 1,000μmor 1 mm Naked eye Eukaryotes 10-4 100m 10-5 10m Bacillus megaterium 10-6 1.000 nm or Prokaryotes 1 um Escherichia coli 10-7 100nm Light microscope Mycoplasma 10-8 10 nm Virus Viruses 10-9 1nm Electron microscope size comparison of microorganisms Meters Visibility scale Relative size of Microbes Prokaryotes Eukaryotes Viruses Naked eye Light microscope Electron microscope