It seems to be well known that life cannot arise in a racemic mixture of molecules (L=D). The various physical mechanisms that could influence the homochirality of the molecules responsible for life are reviewed together with a model where these molecules might be produced in the galaxy prior to the formation of the earth. The focus is on the influence of a powerful supernovae explosion to affect the homochirality of these molecules. Possible tests of this concept with meteorites and future space missions are described.