How Big is a...?

The head of a pin is about 2mm in diameter. Use this animation to compare the relative sizes of cells and organisms sitting on a pinhead. Nearly invisible without magnification, dust mites dwarf pollen grains and human cells. In turn, bacteria and viruses are even smaller.

How to Use

• Use the left and right arrows to change magnification.
• Click on the magnifications (1, 10, 100...) for a "Power of Ten" zoom.
• Choose an individual cell or organism (right) to bring it into view.
• Use the scale to measure individual cells.

1 millimeter = 0.001 (1 thousandth) meter
1 micron = 0.000001 (1 millionth) meter
1 nanometer = 0.000000001 (1 billionth) meter