The subtleties of nature never cease to amaze me. Even the difference in placement of one molecule in a chemical structure can make a world of difference.
For a fairly simple example of this, check out the National Science Foundation video describing the difference between clove and nutmeg. (Hint: It's only the placement of one double bond.) The chemical formula of their main ingredients (eugenol and isoeugenol) is the same (C10H12O2), yet extensive expeditions and even wars were started over the search and possession of these spices in the ancient world.
Cinnamon (cinnamaldehyde) is quite a bit different since its chemical formula (C9H8O) and structure are more complex. But, I pair cinnamon with cloves and nutmeg regularly during my holiday chemistry experiments known as baking. And the taste buds sit up and take notice of this chemical combo. How about you? What are your favorite spices to combine? Go Science!