Summary Note
Key concept recap
What is a Cell?
The cell is the fundamental structural and functional unit of all living organisms. Unicellular organisms can perform all essential life functions independently within a single cell, while multicellular organisms are composed of many cells working together. Antonie Von Leeuwenhoek first observed and described a live cell, and Robert Brown later discovered the nucleus.
The invention and improvement of the microscope, culminating in the electron microscope, revealed the detailed structural organisation of the cell. Anything less than a complete cell structure cannot sustain independent life, which underscores the cell's central role as the irreducible unit of biology.