Combining two conventional materials with distinct coefficients of thermal expansion at the microscale enables fabrication of metamaterials with negative

zero

or custom-designed thermal expansion coefficients

thereby mitigating harmful structural deformations and thermal mismatches in high-end industrial equipments. As a major branch of mechanical metamaterials research

these structures are evolving rapidly toward multifunctionality. Their chief advantage lies in high designability (tunability)

which permits on-demand property customization. Fundamental realization principles and control mechanisms of tunable thermal-expansion metamaterials are elucidated

followed by a systematic overview of advances in mechanical reinforcement

integration of unconventional properties

dynamic performance regulation

and controllable thermal-expansion superstructures. Current design methodologies

especially the pivotal role of topology optimization in innovative configuration development

are then examined. The selected aerospace applications highlight practical potential. Key research challenges are identified

and future development trends are proposed.