Aroma or odour depends on the shape of molecules !

An odor or odour is a volatilized chemical compound, generally at a very low concentration, that humans or other animals perceive by the sense of olfaction. Odors are also called smells, which can refer to both pleasant and unpleasant odors. The terms fragrance, scent, and aroma are used primarily by the food and cosmetic industry to describe a pleasant odor, and are sometimes used to refer to perfumes. In contrast, malodorous, stench, reek, and stink are used specifically to describe unpleasant odors.[...]

Intersting Studies on odour or Aroma

• Shape Changes In Aroma-producing Molecules Determine The Fragrances We Detect: Shakespeare wrote "a rose by any other name would smell as sweet." But would it if the molecules that generate its fragrance were to change their shape?[1]
• Coffee's Aroma Kick-starts Genes In The Brain: Drink coffee to send a wake-up call to the brain? Or just smell its rich, warm aroma? An international group of scientists is reporting some of the first evidence that simply inhaling coffee aroma alters the activity of genes in the brain.[2]
• How The Nose Knows: Research On Smell Boosted: In the ancient oceans of early earth, three billion years ago, a single-celled creature dropped organic chemicals as it went about its daily business. Unnoticed by the tiny animal, its lost chemicals left a trail that was sensed by a predator. The predator stalked, attacked and ingested its hapless prey -- and the faculty of smell began its long evolutionary development. The sense of smell, notes LSU biology professor John Caprio, originally evolved to detect water-soluble chemicals like amino acids. The ability to detect volatiles in air is an adaptation of the original mechanism.[3]