Spectroscopy
Spectroscopy' is the study of light as a function of length of the wave that has been emitted, reflected or shone through a solid, liquid, or gas. Many times it is analyzed when the chemical is heated, because it makes a special color of flame. Most chemicals make a different color or spectrum than other chemicals. This can be used to see what chemicals are in a substance. Spectroscopy allows scientists to investigate and explore things that are too small to be seen through a microscope, such as molecules, and the even smaller subatomic particles like protons, neutrons and  electrons. There are special instruments to measure and analyse these light waves.