The nucleic acid component of a virus can be made up of six different configurations of either DNA or RNA, but never both. You can classify these different configurations according to the Baltimore Classification system, explained in more detail later on this page. They construct a shell around the virus known as the capsid. The capsid can take on several shapes. There are viruses that are comprised of both icosahedral and helical rod components resulting in shapes that often look like a lunar lander.
Viral components assemble spontaneously within a host cell.
The complete viral construct is called a virion. The virion is the completed, infective virus particle. A virion can be either naked, or enveloped. An enveloped virus is surrounded by a lipid bilayer where a naked virion has no layer. There are seven main classifications of viruses within the Baltimore Classification system.