How Your Brain Understands What Your Ear Hears

How small is a hair cell? Really, really small! With the help of a scanning electron microscope, a microscope that uses electrons instead of light to magnify objects, we are able to zoom in on the bristle-like stereocilia that sit on top of hair cells.

Diameter of hair cell: approximately 10 µm (micrometers) or one-tenth the diameter of an average human hair. (One micrometer is one millionth of a meter.)

Diameter of one stereocilium: approximately 250 nm (nanometers) or one-four-hundredth the diameter of an average human hair. (One nanometer is one billionth of a meter.)

Note: an average human hair is roughly 100 micrometers thick.