The olfactory system is a phylogenetically old system that is connected to brain structures implicated in memory formation and motivational aspects of behaviour. Not surprisingly, odours can provoke vivid memories of past experiences coupled with intense emotions. The importance of olfaction to human beings is emphasised by the evolutionary conservation of a large number of genes dedicated to odour perception. In daily life, odours are essential to nutrition, safety, social interactions and our general sense of well being. Since the identification of odorant receptor genes by Linda Buck and Richard Axel in 1991, for which they were awarded the Nobel prize in Physiology or Medicine in 2004, giant leaps have been made in the understanding of the …