I am sure you have had occasion to be at a fine restaurant and approached by the wine steward with the question…’Do you want to let the wine breathe before dinner?’  As you gaze up from your menu, maybe a bead of sweat would appear on your forehead as everyone at the table pauses for your response.  Oh the pressures of dinning and wine!  Let’s keep it simple…Now typically when a wine is exposed to air it will hopefully become more expressive, but simply uncorking the bottle is not enough exposure to oxygen to effect a major change in the structure.  My response to the steward would depend on the bottle of wine, it’s vintage and grape varietal.  Sometimes I would say the wine could be immediately poured into the glass and other times I would request it be decanted first.  The whole concept of letting wine breathe, is simply to maximize your wine’s exposure to the surrounding air. By allowing wine to mix and mingle with air, the wine will typically warm up and the wine’s aromas will open up, the flavor profile should soften and mellow out a bit and improve the overall intensity.  Typically red wines are the ones to benefit most from breathing before serving. However, there are select whites that will also improve with a little air exposure and as they warm up in the glass. In general, I have found that most wines will improve with as little as 15-20 minutes of air time.  A bottle of wine has traveled a long distance from grape to glass with  and is deserved of being treated with respect, so why not let it breathe!?!  However, after doing a little research I found that in fact, some wines don’t particularly benefit from the practice of ‘breathing’ and a few might actually suffer from it, especially if you are pouring an older wine that is already fully mature.  An older wine may have become fragile with age and give up its flavors quickly after it is poured.  I have experienced this with some age old vintages with very big price tags…the wine was simply gone the instant it was poured into the glass!  No body, thin on flavor and weak aromas.  Allowing a wine to breathe seems to work best and awaken wines that are in their youth, before they are really ready to consume.  Young wines are often ‘tight’ or may seem closed or not accessible, showing little aroma or flavor…they also may be tannic which mellows given time.  At times you may not have a decanter readily available and in that case I like to pour a small bit of wine into my glass and ‘coat’ the glass and then I will pour the wine to the largest portion of the glass there by allowing air to hit as much wine as possible and just let it sit a few minutes before drinking.  Wines with high tannins, Cabernet’s, Syrah’s, will generally need more time to breath whereas lighter bodied wines like Pinot Noir’s may need little or no time at all.  To me wines are never ‘static’…they evolve on the vine, in the barrels, bottle and glass, and as your meal progresses, so has your wine!  Have some fun and experiment with this concept!