A microsecond is an incredibly tiny unit of time: one millionth of a single second. To picture how short this is, imagine blinking your eye. That blink takes about 100,000 microseconds. In just one microsecond, light travels about 300 meters, roughly the length of three football fields.

Computers operate on microsecond timescales. When you click a mouse or tap a keyboard, electronic signals zip through circuits in microseconds. Modern computers can perform millions of calculations in the time it takes you to snap your fingers once.

Scientists and engineers use microseconds when measuring extremely fast events: how quickly electricity flows through a wire, how long it takes sound waves to bounce off a wall, or the precise moment a camera's shutter opens. A high-speed camera might capture 100,000 frames per second, meaning each frame lasts only 10 microseconds.

People sometimes use microsecond informally to mean “an incredibly short time,” as in “Wait a microsecond, I need to think about this.” Though technically inaccurate (they probably mean a few seconds, not one millionth of a second), it captures the feeling of something happening almost instantaneously.