# What is the process by which atoms are arranged to form a material with a crystal shape called?

$\text{Crystallization}$.
$\text{Crystallization}$ remains the premier means to purify an inorganic or organic material. You get crystals out and you know your stuff is pure (of course, your material may crystallize out as a solvate, i.e. the crystals occlude several solvent molecules).
Good quality crystals allow an $\text{X-ray crystallography experiment}$ to be performed, which is a very non-sporting method of analysis.