Structural adhesives are used increasingly in new applications replacing conventional joining methods. Epoxy adhesives have the widest range of application of the various classes of adhesives arising principally from their extremely wide set of performance properties. They are known for their high stiffness and strength, as well for their low ductility and toughness. Currently, there is an increasing interest in developing methods of improving toughness. A toughened adhesive in general contains elastic or thermoplastic domains dispersed in discrete form throughout the resin matrix, in order to increase the resistance to crack-growth initiation. This paper provides an overview of the current developments in the use of reinforcement materials and introduces the reader to early findings on the use of micro particles for toughness enhancement of adhesives. The theme of the use of materials of natural origin as reinforcement materials, giving special emphasis to the use of cork particles as toughener material is also presented.