Capsid is the protein shell or coat of viruses that encloses the genetic material. Capsid is made-up of monomeric units called capsomere, these are several oligomeric (repeating) structural subunits made of protein. In TMV (tobacco mosaic virus), single-stranded RNA is enclosed by a capsid that is made of 2,130 sub units called capsomeres. There are 49 capsomeres on every three turns of the helix.

The nucleoid is a "nucleus-like" genetic material that is an irregularly shaped area in the prokaryotic cell without getting enclosed by a nuclear membrane. Nucleoids generally contain a single pair of chromosomes. The genetic material inside the nucleoid is very long in size and undergoes supercoiling to fit within the nucleoid.

Fossils are the remains or traces or impression of ancient life or once-lived organisms that have been preserved by natural processes. Fossils are formed when a living organism dies and is quickly buried by sediment that lived millions of years ago.