Size and shape

Viruses are ultramicroscopic - far too small to see with an ordinary light microscope - typically ranging from about 20 to 300 nanometres across (1 nm = 10^-9 m). A bacteriophage is roughly 10-100 nm, while TMV measures about 300 x 20 nm. Based on their overall shape and symmetry, viruses fall into three broad groups: cuboidal symmetry (e.g. Adenovirus, Herpes virus), helical symmetry (e.g. Influenza virus, TMV), and complex or atypical symmetry (e.g. Bacteriophage, …