Science is haunted by an enigma: Amino acids, which make up living matter, are able to exist, chemically speaking, in two forms, a left and a right, like our two hands, yet strangely enough they are all found to belong to the same "hand." Pasteur said that these natural molecules were "dissymmetrical." Another discovery has just reopened the question. The Universe itself, we find, is characterized by a decisive break in symmetry, one that has given matter the upper hand over antimatter. Thus, the scenarios of the astrophysicists fall in line with the findings of the molecular biologists - a line running from the cosmos to life. The practical implications of the "direction" of life are enormous. In the laboratory we can synthesize compounds in both the "left-handed" and "right-handed" forms, but the effectiveness of an insecticide or a drug, for example, as well as their side effects, depend on the "doubling" of the molecule of which they are composed: "right" and "left" are not the same thing.