A cell is small, and it is packed shoulder to shoulder.

Two interactive figures are below: one for how the pieces of a cell compare in size across seven orders of magnitude (powers of ten), and one for how crowded it gets in the cytosol.

Scale

Every tick on this ruler is ten times the last. Pick an object to see its real size, how many would span a 25 µm liver cell, and what it would look like if that cell were inflated to a 100 m stadium.

Real size

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At stadium scale

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Fit across one cell

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Crowding

Cytoplasm holds roughly 300–400 mg/mL of protein, RNA and complexes, filling 20–40% of its volume. This is a to-scale slice 200 nm wide. Raise the occupied fraction and watch the open water disappear.

Volume occupied 30%

Ribosomes, 25 nm Large complexes, 10 nm Proteins, 5 nm Field: 200 × 100 nm

Macromolecule concentration

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Average protein-to-protein gap

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That gap, in water molecules

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Concentration assumes a protein density of 1.35 g/mL. The gap treats 5 nm proteins as evenly spaced spheres, so it is a mean-field estimate. The slice is a 2D random packing, which understates true 3D crowding slightly; the size mix is split by volume and loosely follows E. coli.