Ecobionanocomposites are a new class of materials based on ecologically friendly resources derived by biotechnological means and customized for specific applications by exploiting nanotechnology. This technological triple convergence of two rapidly expanding fields with ecological considerations offers hope for addressing pressing environmental and sustainability issues. Polylactide (PLA) is a polyester derived from renewable resources utilizing biotechnological techniques and can degrade under appropriate conditions. In addition to its ecological value, it has gained increasing attention due to its recent economical attractiveness, especially in the light of increasingly expensive petroleum based resins. Cellulose is the most abundant form of living terrestrial biomass, and it is a host of important properties including structural hierarchy at the nanoscale. In previous work, we developed a novel approach towards composites by using reactive groups on the surface of cellulose fibers at the microscale to initiate the polymerization reaction of lactide. Through the use of reactive compatibilization, many of the limitations of a two phase composite were overcome. A similar strategy is applied to nanosized cellulosic fillers originating from acid hydrolysis of cotton linter. The chemistry of creating these novel and ecologically responsible, bio-inspired and derived nanocomposites is described. Thermo-physical and mechanical properties of these novel materials are discussed, and it is demonstrated that the use of reactive compatibilization offers unique opportunities in creating new and value added materials.