In an immensely powerful magnet, pulses of radio frequency waves make individual atoms within the body dance to the scanner’s tune. The tiny signals emitted by the atoms as they realign with the magnetic field are detected and used to peer into the tissues inside the body. The technique has many applications, as can be seen in this set. It can be used to identify tumours, show blood vessels, bleeding in the brain and damage to nerves, amongst other things. Such diagnoses have saved many lives, and the 2003 Nobel Prize for Physiology or Medicine was awarded for the development of the imaging technique.