= X-ray crystallography
{c}
{tag=Crystallography}
{wiki}
One of its main applications is to determine the 3D structure of <proteins>.
Sometimes you are not able to crystallize the proteins however, and the method cannot be used.
Crystallizing is not simple because:
* you need a considerable amount of the protein
* sometimes it only crystallizes if you add some extra small chemical that stabilizes it
<Cryogenic electron microscopy> can sometimes determine the structures of proteins that failed crystallization.