Diatoms are key players in aquatic ecosystems and the global carbon cycle, known for their silica-based cell walls (frustules) that provide mechanical protection. This study investigates the strength of diatom frustules, revealing their remarkable durability due to both architectural design and silica material properties. Experiments using calibrated glass microneedles and finite element analysis showed that frustules can withstand high forces, with some species resisting up to 730 μN. The frustules' structure, including transverse ribs (costae), helps distribute stress and absorb mechanical impacts, making them highly resistant to breakage. The silica in diatom frustules has a Young's modulus of 22.4 GPa, comparable to cortical bone, indicating high tensile and compressive strength. These properties suggest that frustules evolved as effective armor against predators. The study also highlights the evolutionary arms race between diatoms and their predators, influencing food webs and biogeochemical cycles. The frustules' complex structures resemble man-made materials, suggesting they serve as physical protection. The research underscores the importance of diatom frustules in ecological roles, as they provide mechanical defense against predators, contributing to diatom dominance in phytoplankton blooms. The findings emphasize the significance of diatom frustules in ecological and evolutionary contexts, highlighting their role in the ocean's biological carbon pump and food chains.Diatoms are key players in aquatic ecosystems and the global carbon cycle, known for their silica-based cell walls (frustules) that provide mechanical protection. This study investigates the strength of diatom frustules, revealing their remarkable durability due to both architectural design and silica material properties. Experiments using calibrated glass microneedles and finite element analysis showed that frustules can withstand high forces, with some species resisting up to 730 μN. The frustules' structure, including transverse ribs (costae), helps distribute stress and absorb mechanical impacts, making them highly resistant to breakage. The silica in diatom frustules has a Young's modulus of 22.4 GPa, comparable to cortical bone, indicating high tensile and compressive strength. These properties suggest that frustules evolved as effective armor against predators. The study also highlights the evolutionary arms race between diatoms and their predators, influencing food webs and biogeochemical cycles. The frustules' complex structures resemble man-made materials, suggesting they serve as physical protection. The research underscores the importance of diatom frustules in ecological roles, as they provide mechanical defense against predators, contributing to diatom dominance in phytoplankton blooms. The findings emphasize the significance of diatom frustules in ecological and evolutionary contexts, highlighting their role in the ocean's biological carbon pump and food chains.