Solid-state chemistry
Once the unit cell of a new phase is known, the next step is to establish the ratio of the elements (stoichiometry) of the phase. This can be done in a number of ways. Sometimes the composition of the original mixture will give a clue, if one finds only one product (a single powder pattern) or if one was trying to make a phase of a certain composition by analogy to known materials.  But this is rare.