In a Science article (DOI: 10.1126/science.1249168) C. Bushdid, M. O. Magnasco, L. B. Vosshall, A. Keller determine the size of the olfactory repertoire. On the basis of psychological testing they find that the human nose can distinguish at least 1 Billion (european enumeration = 1012) In the English nomenclature leaving out Milliarde (109) this is even more impressive: 1 Trillion. I wonder about the number of chemically defined receptors. In the case of the immune systems the repertoire of B and T cells (1012) could finally be explained by recombination. What the olfactory system has in its stores is to be seen. This paper sets the threshold fairly high.