Bacteriophage
Phages are typically made of an outer protein hull that has genetic material inside it. The genetic material may be single-stranded (ssRNA or ssDNA), or double-stranded (dsRNA or dsDNA). It may be between 5,000 and 500,000 base pairs long with either circular or linear arrangement. Bacteriophages are usually between 20 and 200 nanometers in size.