Nature has evolved exceptional structural materials—such as nacre, bone, and the mantis shrimp’s dactyl club—that achieve remarkable combinations of strength, toughness, and impact resistance through intricate synergy of structure and composition. Inspired by these biological systems, this work presents a comprehensive investigation into bioinspired materials, uncovering fundamental mechanisms and providing guidance on the design of nanocomposite materials with superior mechanical properties. We first explore the "brick-and-mortar" structure of nacre, which inspired the fabrication of layered polymer-graphene nanocomposite films. Through coarse-grained molecular dynamics computational analysis, we elucidate the dynamic wave propagation and energy dissipation mechanisms in such type of nanocomposite films. Our analysis reveals that the reflection and superposition of shock waves critically influence film deformation and initiate polymer crazing. Additionally, we find that the irreversible deformation of the polymer phase is the dominant mechanism of energy dissipation. The highest energy dissipation efficiency occurs when the polymer undergoes moderate deformation. Those findings provide key insights for designing lightweight, impact-resistant structures. Building on the impact-resistant dactyl club of the mantis shrimp, we propose the nanoparticle-polymer nanocomposites which considers three different types of nanoparticles: smooth, corrugated, and porous. It turns out that the addition of nanoparticles introduces dynamic heterogeneity into the nanocomposites through interfacial interactions and the unique structural confinement effect of the porous nanoparticles. Moreover, the stronger the interfacial interaction, the greater the dynamic heterogeneity. The dynamic heterogeneity enables the nanocomposites to overcome the conventional stiffness-damping tradeoff, achieving concurrent enhancements in stiffness, strength, and energy absorption—a critical advancement for protective materials and structural applications. Shifting focus to human tissue, we first look at bone’s microstructure which can be resembled by freeze casting to fabricate biomimetic scaffolds. Combining 3D print, finite element modeling, and mathematical theory, we establish predictive relationships between scaffold architecture and mechanical properties, enabling the rational design of such scaffolds. Furthermore, we investigate the tendon-bone insertion—a natural gradient material that seamlessly bridges two mechanically dissimilar tissues: stiff bone and compliant tendon. Given the persistent challenge of creating robust interfaces between dissimilar materials in engineering systems, the tendon-bone insertion offers valuable design insights with its unique graded interface. Through systematic analysis of its structure-composition-property relationships, we elucidate the mechanisms governing its exceptional load transfer capability and damage tolerance, with the ultimate goal of translating these biological design principles into innovative strategies for engineering dissimilar material interfaces. This research provides a potential framework that could contribute to the design of high-performance material systems. Our findings not only deepen the understanding of natural materials but also provide practical pathways to engineer advanced materials for applications ranging from aerospace to biomedical devices.