The term "superstructure" was introduced to describe the structure of ordered solid solutions. Superstructures are formed below a certain temperature (called the "order-disorder transition temperature") in cases where atoms of a certain sort are energetically preferable to be surrounded by atoms of another sort. Superstructures often originate as a result of second-order phase transitions. The formation of superstructures is accompanied by the appearance of weak additional superstructure lines in diffraction patterns used to detect and identify the type of superstructures.

One example of a superstructure is the structure of Cu-Zn alloy (brass) where in the disordered state Cu and Zn atoms are distributed with equal probability over the nodes of the body-centred lattice, and in the ordered state atoms of one type occupy nodes at the corners of cubic cells and atoms of the other type – in their centres.

Often the term "superstructure" is used to denote a structure where the growth of lattice defects (impurity atoms, vacancies, etc.) makes these defects orderly placed. Normally, this ordering is accompanied by reduction in the crystal lattice symmetry (see the Figure).