Some of the metapsychology involving the concept of structure is briefly reviewed, together with some difficulties presented by it. The concept of structure is defined, for purposes of the paper, and various kinds of structures are delineated. The author confines herself to the "microstructures," such as memories, cognitive structures, affect structures, defenses, identifications. Possible factors related to the development and maintenance of structures are discussed. In addition, the concept of structural change is taken up. It is suggested that an essential in such change is conscious review, however brief. The author proposes that structure formation and change is a fruitful area for mutual work by psychoanalysts and basic scientists.