Imagine a world where you couldn’t smell your favourite food cooking, or the scent of perfume or aftershave or ﬂowers. Think of what it’s like when you have a cold – your nose is blocked and you lose your sense of smell. When that happens you often cannot taste either, so you lose your appetite. Equally think of smells that are not so pleasant, like smelly socks or rotting ﬁsh. All of them have one thing in common - they are caused by speciﬁc molecules interacting with the nasal sensory receptors.