Appliance of Science: How are smells made?

This week’s question comes in from Rob in Co Clare; he would like to know how smells are created and how they travel.

You have probably heard that humans have a poor sense of smell compared to other animals and that it is less important than some of our other senses, but that’s not true at all; smell is a fascinating sense, it triggers our memories and emotions and is the first sense we use at birth. Let’s start with the basics.

How are smells made?