Medicine
Ultrasound Imaging
Quick fact
Ultrasound uses frequencies between 2 and 18 megahertz, far above human hearing, and can capture moving images in real time, like a beating heart or a fetus kicking.
Why this is interesting
You've probably seen a grainy black-and-white image of a baby before birth—but how does ultrasound see inside the body without any X-rays or radiation?