Materials with variable constitutive properties hold great potential for enhancing performance under diverse working conditions. Moreover, advances in manufacturing technologies have made it feasible to produce such variable constitutive materials and structures (Fig.1). Topology optimization addresses the presence or absence of material, which can be interpreted as two distinct property distributions—special cases within the broader material property space considered by constitutive optimization (Fig.1 D). Constitutive optimization is based on property variation. Materials may undergo irreversible property changes when subjected to external stimuli (Fig.1 E). The main purpose of optimization has been shifted from material distribution to property distribution (Fig.1 F). Consequently, constitutive optimization operates in a higher-dimensional space, offering a larger design space, more versatile material interpolation models, and greater design freedom. Our preliminary findings indicate that constitutive optimization is both necessary and effective, enabling the optimal distribution of material properties and leading to significant performance enhancements.