An Introduction to Cells and Viruses Introduction to Cells and Viruses Cells are the principle means for study in the subject of Cellular and Molecular Biology. They are the fundamental structural units of all living organisms. A cell is very small, usually invisible to the human eye.
Cells can also move, duplicate, and alternate their biomedical reactions.
In the most structured organisms, different tasks are divided by groups of specialized cells, whereas in bacteria and protozoa, each cell is independent and capable of carrying out all activities of life.