Viruses are smaller than a photon, the smallest particle of light, and cannot be seen with a normal optical microscope. It wasn’t until the 1930’s, when the electron microscope was invented, that we could see what viruses look like. An electron microscope fires electrons at an object and a computer interprets how they interact with it to produce an image of the object.
A virus is a parasite. Entry, genome replication, and exit are the phases of a viral life cycle. Entry involves attachment, penetration, and the uncoating or shedding of the capsid. After the virus has replicated itself, it assembles to form a particle to facilitate its exit or release from the host.
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