Book excerpt: Composites are used in a wide range of applications, from electronics to the aeronautical industry. The excellent mechanical properties and low-specific weight of composites are the basis of many structural applications. Despite the progress achieved, there are significant obstacles to the generalisation of structural applications of composites, mainly due to their high cost and complex mechanical behaviour. In fact, there is currently insufficient knowledge regarding the mechanical properties and failure mechanisms of composites made from renewable and sustainable materials. This book focuses on composites from natural and renewable resources, including the enhancement of their properties with additives such as biodegradable nanomaterials, their mechanical characterisation, tailoring of properties for specific applications and their processing.