Metallurgy
Metallurgists use many tools to  determine the characterizes of metal using a technique called metallography. One of the most useful tools is the Scanning Electron Microscope. To use an SEM a metal sample is polished and hit with electrons to produce a clear image of the metal. This permits for the metal microstructure to be seen.  A  microstructure is what the metal looks like when zoomed in very closely. There are many types of microstructure such as pearlite and ferrite.