# Cell

The smallest unit of life. Every living thing is made of one or more cells.

Biology (school) · Part 01: Cells · Card 1 of 12 · Last updated 2026-10-19

## Analogy

A cell is like a single brick. A body is a huge wall of bricks.

## In practice

Your skin, blood and muscles are all made of cells working together.

## Questions people ask

### Who discovered cells?

Robert Hooke first described cells in 1665 when he looked at thin slices of cork through an early microscope. He saw tiny box-like spaces and called them cells. Later scientists found that all living things are made of cells, which became known as cell theory.

### Are there living things with only one cell?

Yes. Bacteria, yeast and amoeba are single-celled organisms. That one cell does every job needed for life, including feeding, getting rid of waste and reproducing. Most plants and animals are multicellular, which means many cells share the work and each type has its own job.

## Related concepts

- [Nucleus](https://studyvisually.com/learn/science/biology-school/biology-school-part-1/biology-school-part-1-concept-2)
- [Cytoplasm](https://studyvisually.com/learn/science/biology-school/biology-school-part-1/biology-school-part-1-concept-3)
- [Cell membrane](https://studyvisually.com/learn/science/biology-school/biology-school-part-1/biology-school-part-1-concept-4)
- [Mitochondria](https://studyvisually.com/learn/science/biology-school/biology-school-part-1/biology-school-part-1-concept-5)

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