Our body is made up of a gazillion atoms spinning around each dancing to their own drummer. When these atoms are excited with a really strong magnet, like an MRI machine, they all line up at attention. When they are then hit with a radio wave, they are knocked down and scattered. While they are getting back in line again, each atom sends out very distinct signals. These different signals indicate where each atom lives like the kidney or liver since each has a unique characteristic signal intensity. The signals are captured by detectors and processed by computer. The entire process is called magnetic resonance imaging or MRI. MRIs are great for looking at all the soft and squishy parts of the body like organs and tissue that x-rays don't see.