When you experience a glass of red wine, for example, you may enjoy its dominant cherry aroma—until someone comments on a strong vanilla note in the same glass of wine. Suddenly the cherry moves to the backseat of your conscious awareness, while the vanilla aroma pops into focus—even though you had not noticed it before. How do you turn such ephemeral and transient nature of odors into a measurable, stable, and comparable object of scientific study?