<p>With the exponential growth of digital information, it is essential to move beyond single storage states and develop multilevel storage for high-density memory devices. However, systematic strategies for constructing multilevel memories remain underexplored. This review summarizes key approaches from both intrinsic material design (<i>e.g.</i>, coupling multiple memory mechanisms, introducing electronic defects, functional group modification, charge-trapping engineering, and redox center design) and extrinsic regulation (<i>e.g.</i>, tuning testing parameters, applying light/irradiation/magnetic fields, doping, and size effects). Furthermore, diverse functional materials have been employed, including inorganic compounds, organic and polymeric materials, low-dimensional systems, and functional materials, such as magnetoelectric, biomaterials, and composites. We suggest that continued attention to multilevel memory applications will accelerate progress and inspire further advances in this field.</p>