MRI stands for Magnetic Resonance Imaging. It is a special kind of medical test that helps doctors look inside your body. During an MRI, a big magnet and radio waves are used to take pictures of the inside of your body. The MRI machine is like a big tube that you lie down inside. The magnet makes your body's atoms send out signals, and the computer in the MRI machine reads the signals and turns them into pictures. Doctors look at these pictures to see if there is something wrong inside of your body.