A research on interactive generation of visual composition is described here. This paper introduces MasterPiece, an evolutionary environment implemented as a tool for manipulating visual structures using genetic algorithms. MasterPiece allows to evolve visual compositions and also to genetically manipulate, edit, store and recover them, acting as a laboratory for experiences applied to the visual composition. Visual compositions are considered here as two-dimensional images generated by the computer by combining pre-defined shapes inspired in a Kandinsky artwork. Some visual results are presented.