The human brain is a truly staggering piece of anatomy/machinery. There are so many things it does that we don't pay attention to, things that become second nature. Smell is one of those things; it's a sense that we use without thinking. We come across different smells every day, some pleasant, some not and unconsciously our brains register these smells and attach information to them.
As a writer I'm learning that smell is essential. Recently I happened to get some new perfume, one that I used to wear when I was a teenager. As soon as I sprayed it memories flooded back and I was transported 17 years into the past. Butterflies fluttered in my stomach, I closed my eyes and breathed in the scent. Emotions cursed through me and as I thought about my novel I was inspired to write about a particular character. It was this that made me realise how important smell is for writers.