NMR spectroscopy
A chemical sample is prepared by placing a tiny amount of the sample in an NMR tube. It is dissolved in a special solvent like heavy water (see deuterium) or chloroform-d, then the tube is placed into the NMR machine. The machine is a large magnet, like an MRI. Some atoms in the sample will become excited when it is in the magnet, and when the sample is removed, the atoms will go back to a lower energy state. A computer connected to the NMR can detect this change in excitement and it will cause different peaks and bumps to appear on the NMR diagram. A chemist can print this diagram and study the various peaks.