This Critical Review provides an overview of the recent developments in the synthesis and characterization of bimetallic nanoparticles. Initially the review follows a materials science perspective on preparing bimetallic nanoparticles with designer morphologies, after which the emphasis shifts towards recent developments in using these bimetallic particles for catalysing either oxidation or reduction. In the final part of this review we present an overview of the utilization of bimetallic catalyst systems for the transformation of bio-renewable substrates and reactions related to the realization of a bio-refinery. Because of the sheer number of examples of transformations in this area, a few key examples, namely selective oxidation, hydrogenation/hydrogenolysis and reforming of biomass derived molecules, have been chosen for this review. Reports of bimetallic catalysts being used for the aforementioned transformations are critically analysed and the potential for exploiting such bimetallic catalysts have also been highlighted. A specific objective of this review article is to motivate researchers to synthesize some of the "designer" bimetallic catalysts with specific nanostructures, inspired from recent advances in the area of materials chemistry, and to utilize them for the transformation of biomass derived materials that are very complex and pose different challenges compared to those of simple organic molecules. We consider that supported bimetallic nanoparticles have an important role to play as catalysts in our quest for a more green and sustainable society.