People's favourite smells are usually associated with childhood memories and emotion, according to one expert.
Physicist and science communicator Phil Smith was speaking as the smell of bacon sizzling on the pan was revealed as people's favourite scent.
A new poll found half of people surveyed put the fry smell top of the list - followed by freshly baked bread, coffee, rain on the street and roses.
Other popular smells include a wet dog, tennis balls, blue cheese and Deep Heat.
Phil told Lunchtime Live where this all comes from.
"It's one of our special senses and we use it for lots of different things.
"Not only looking for desirable foods but identifying hazards, pheromones and a massive role in taste.
"Smells are handled by an olfactory bulb which is the structure in the brain that sends information to other parts of the body for processing.
"Odors or smells - we take them in, we absorb them into our limbic system.
"[It] has a strong connection with emotion and memory, and it's basically one of the things that we use to identify things in the world that are either useful to eat, that are going to be dangerous to us - or things that we need or should be attracted to".
'Smell and emotion'
He says a sense of smell is one of the first things we have.
"Smell is the only fully-developed sense a foetus has in the womb, and it's one of the things that's mostly developed in us as a child.
"Until around the age of 10, before sight takes over.
"This is why smell and emotion are kind of very strongly linked to us: it's where we develop in our childhood a lot of what our tastes, and how we connect to things, to the emotions that come with these smells.
"What we do as humans, the connection between memory and emotion makes smells unique from our other senses.
"You might catch a whiff of something, and instantly be transported to a different place or time in your past.
"You might think of someone baking or the smell of a crayon, or even the smell of a perfume an ex used to wear - it creates that connection".
