An overview on structure, processing and application of natural and biological materials, biomaterials for biomedical applications, and fibre-reinforced eco-composites based on renewable resources will be provided. Fundamental principles related to linear elasticity, linear viscoelasticity, dynamic mechanical response, composite reinforcement mechanics, and time-temperature correspondence will be introduced. Novel concepts in comparative biomechanics, biomimetic and bio-inspired material design, and materials' ecological and environmental impact will be discussed. In addition, key material processing methods and testing and characterization techniques will be presented. Structure-property relationships for materials broadly ranging from natural materials, including wood, bone, cell, and soft tissue, to synthetic composite materials for industrial and biomedical applications will be covered.