Experimental petrology can range from creating artificial magmas to measure crystallization behavior to observing recrystallization of minerals at varying pressure/temperature conditions.
Although methodology varies from experiment to experiment, in general the procedure involves evaluating a synthetic rock or magma (created from a blend of oxides to replicate the chemistry of the rock/system in question) in an apparatus capable of creating and sustaining high pressures and temperatures such as a diamond anvil cell.
Standard procedure generally involves the creation of a synthetic magma (often corresponding to a real world analog) which is then cooled to a target temperature.
Fractional crystallization studies represent a fairly recent trend in experimental petrology, gaining popularity as a way to more accurately depict magma evolution in scenarios where a cumulate layer is built.
In such a manner it is possible to examine the behavior of a magma body as it slowly cools and crystallizes over time.