US scientists Mr Richard Axel and Ms Linda Buck won the 2004 Nobel prize for medicine or physiology today for work on genes that control the sense of smell.
The two, who published their fundamental study in 1991, found a gene pool that contains the blueprint for receptors or sensors in the nose that identify odours in investigating how people can recall, months later, the scent of a lilac.
"The sense of smell long remained the most enigmatic of our senses. The basic principles for recognizing and remembering about 10,000 different odours were not understood," said the Nobel Assembly of Stockholm's Karolinska university hospital, in its citation for the 10 million crown (€1.1 million) award.
"Until Axel and Buck's studies the sense of smell was a mystery," said Professor Sten Grillner of the Karolinska's panel.
The two described a large family of 1,000 different genes, 3 per cent of the total in the human body, that give rise to an equivalent number of sensors in the nose that identify smells, known as "olfactory receptor types".
These sensors sit on cells in the back part of the nose and are responsible for identifying smells. Each receptor cell has only one type of odorant receptor, which can detect a limited number of types of smell.
The receptor cells then send signals back to the parts of the brain responsible for smell.
"Therefore, we can consciously experience the smell of a lilac flower in the spring and recall this olfactory memory at other times," the citation noted.