01Size2.00 µm
Bacterium
Single-celled life, no nucleus required.
BiologyMicrobeMicro-World
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TenOfAllTrades (CC BY-SA 3.0)
Cell Human hair
Drawn to true scale.
Picture this
Scale a cell up to the size of a basketball — at that same scale, a strand of human hair would stand as tall as you do.
A cell is where chemistry becomes biology — a membrane-bound bag of molecules that can copy itself. Your body holds about 30 trillion of them. The smallest bacterial cells are 1–2 µm wide; a human red blood cell is about 8 µm; some single cells, like an ostrich egg yolk, are large enough to hold in your hand.
Did you know?
Your body replaces about 330 billion cells every day. Most of the matter you call "you" is, materially, only a few years old.
Last updated 2026-05-17
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Scale
The smallest unit of life.
Size
10.0 µm
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