If you’ve had a glass of wine with friends, odds are someone has described at as oaky. And perhaps you’ve heard a white wine described as having notes of green pepper.

None of that happens because someone tossed a bell pepper into the wine as it was being fermented. Rather, it happens because of unique flavor, aroma and color compounds that make us just .1 percent of wine. The other roughly 99.9 percent is basically the same from wine to wine: water and ethanol, plus trace amounts of acids and sugars.

And perhaps more than with any other drink, in wine, these tiny characteristics are what separates an average wine from one that is truly great.

“We expect milk to be just like the milk we tried a week ago,” says Gavin Sacks, an associate professor at Cornell University and an expert on wine cultivation. “There is an expectation that wine is going to be different.”

But don’t think that the differences you’re tasting are really being sensed by your tongue. Sacks says with wine, and in general, most of what we call taste is actually coming from our nose.