The receptors of smell

As far as we can tell, all of the olfactory cells, which act as receptors recognized by the smell of chemicals, exactly the same, so it remains a mystery how they distinguish between thousands of diverse scents.
For many centuries people have identified six "core" scents: floral, fruity, smell, spicy, resinous (like turpentine) and the smell of burning.
To have odor, a substance must vaporize microscopic particles. The smallest building blocks of any substance are molecules, and it is believed that the olfactory cells are able to differentiate molecules by their shape.