01Size10.0 µm
Cell
The smallest unit of life.
BiologyMicro-World
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NIAID / Rocky Mountain Laboratories
Bacterium Human hair
Drawn to true scale.
Picture this
Magnify a bacterium until it sits in your palm like a marble — and a single grain of sand at that same scale would tower beside it like an adult human.
Bacteria are the workhorse cells of the planet. They have no nucleus — their DNA floats free in the cytoplasm — and they replicate by splitting in half, sometimes every twenty minutes. The human body holds roughly as many bacterial cells as human ones, and they outnumber every kind of multicellular life put together.
Did you know?
By count, roughly half of all the cells in your body are bacteria. By mass, they only add up to a couple of hundred grams — but without them you couldn't digest a meal.
Last updated 2026-05-17
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Scale
Single-celled life, no nucleus required.
Size
2.00 µm
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