A microorganism that can pass through filters that trap bacteria and can reproduce within a host’s living cells is defined as a virus. The virus particle’s nucleic acid component, along with its surrounding protein shell called the capsid, makes up the nucleocapsid. The capsid is created from a collection of smaller structural protein units known as capsomeres. The process of constructing virus particles from their nucleic acid and protein components is referred to as assembly. The aggregation of virus particles into dense masses that may be crystalline or paracrystalline in form is referred to as aggregation. A virion is a single mature virus particle that, for plant viruses, is frequently equivalent to the nucleocapsid but may also include an additional surrounding envelope. Transcapsidation refers to the enclosure of the genome of one virus within a complete protein capsid of a second virus, which is also known as genomic masking. If the genetic information required for multiplication is divided between two or more physically separate particles, the virus is said to have a divided genome.