We consider aspects of patternings that occur in a wide array of physical systems due to interacting combinations of dipolar, interfacial, charge exchange, entropic, and geometric influences. We review well-established phenomena as a basis for discussion of more recent developments. The materials of interest range from bulk inorganic solids and polymer organic melts to fluid colloids. Often, there are unifying principles behind the various modulated structures, such as the competition between surface or line tension and dipolar interaction in thermally reversible systems. Generally, their properties can be understood by free-energy minimization.