By bringing sensory detail into your writing, you can stir emotion in your characters and in your reader, as well. Sensory detail puts the reader more into the mind and body of the character.
First, let's discuss scent. The nose knows.
My grandmother always wore Jergen's lotion. She passed away almost two decades ago, but one whiff of Jergen's lotion and immediately I experience a sense of security, and the love and happiness I felt whenever I spent time with my grandmother. The scent also brings back memories of how it felt to be a carefree child with a long summer stretching ahead of me, because I most often visited my grandparents during the summer. If I was writing a scene in which I wanted to create those emotions and memories in my character and the reader, I might use Jergen's lotion to do so.
Here's a rather simplistic example of how you might use scent in your writing to trigger emotion, and thereby help your readers connect with and relate to your character.
Let's make our character a woman -- a mother. We'll name her Sue. Sue is having problems with her rebellious, angry teenaged daughter, Heather. Heather blames her anger on her belief that her mother doesn't understand her, or even try to. One day, Heather storms out of the house after an argument, and Sue finds her daughter's car in the parking lot of a nearby mall. Late for a meeting and fed up with Heather's constant antics to get attention, Sue goes inside the mall to look for her daughter, and as she passes a perfume counter in a department store, her senses are filled with the scent of White Shoulders cologne. Sue's mother always wore White Shoulders, and the aroma instantly triggers a memory of being in her mom's bedroom when she was a teenager. She'd been trying to convince her mother to let her go away for the weekend with a couple of friends, but her mom was dressing for a party and was too preoccupied to listen to Sue's reasoning. The memory of the frustration she had felt over her mother's distracted refusal to take the time to talk to her, triggers an emotion of sadness in Sue, and suddenly her anger at Heather transforms into understanding and regret.
Most any reader who is or ever was a teenager will relate to these feelings of being ignored or misunderstood. Whether or not the source of the feelings was real or imagined, every teen has experienced frustration with a parent. And so your reader will relate. And every person associates certain scents with situations or people from their past. So they'll relate to Sue's experience when she smells White Shoulders, as well.
Try this exercise: Choose one of the following every day scents that most people have on hand-- vanilla extract, suntan lotion, or furniture polish. Smell the scent you choose then, using paper and pen, describe it without using scent descriptors. For instance: "The pie smelled of sunshine . . . of warmth and innocence and simpler times." (But you can do better than that. ;-) )