Cocoa is the dry residue that separates from the fat, called cocoa butter or theobroma oil, during the pressing stage. Cocoa is made from cacao, not the other way around. During the cooling process the cocoa butter in chocolate can solidify into one of six different polymorphs. Form V is the polymorph most common in well-tempered chocolate. The other forms feel too sticky or thick in the mouth.
Chocolate bars suffering from fat bloom look dusty or cloudy, taste bland, and melt too easily.
Although form V is the best tasting polymorph of cocoa butter, form VI is the most stable. Food scientists in the chocolate industry seek to develop techniques that encourage cocoa butter to solidify in the form V polymorph. An expert technician can then interpret this pattern and infer the configuration of the solid lattice as the cooling cocoa butter molecules rearrange themselves. Different heating, cooling, and stirring regimes are tested until an optimum process evolves. This is one reason why chocolate melts so well in the mouth.