What is a Cell?

The cell is the basic building block of every living organism — both the smallest unit that has structure and the smallest unit that can actually carry out the work of being alive.

Why the cell is the fundamental unit

Some organisms exist as a single cell, and these unicellular forms tell us something important: one complete cell is enough to survive on its own. A single-celled organism can:

• lead an independent existence, without depending on any other cell, and
• carry out all the essential functions of life by itself.

Because a lone cell can manage both of these, and because anything smaller or less complete than a whole cell cannot support independent living, the cell is recognised as the fundamental structural and functional unit of all living things. In other words, it is the smallest package of matter that is genuinely alive.

How we came to know the cell

Our understanding of the cell grew alongside the tools used to look at it.

• Antonie von Leeuwenhoek was the first to see and describe a living cell.
• Robert Brown later identified the nucleus inside the cell. …