At first glance, key limes are hard to resist. Bright green, shading to lemon yellow, smooth and compact, they're adorably cute - yeah, cute, just like a little puppy. It's hard not to want to snatch a bag or two along with your other groceries.

Of course, once you have gotten them home, you have to use them. You can break out the cocktail shaker - a no-brainer - key limes often have been referred to as the "bartender's lime," and they readily complement a host of libations. But then what? Fix margaritas for a small party and you still might be left with several cute little limes, sitting sadly alone on your counter. What to do?

You might be tempted to substitute them for the larger limes, lemons, or even some other citrus in a recipe, but be careful, because these cute little puppies pack a powerful bite.

Pair them with the right ingredients, however, and they can add depth and dimension to an otherwise ordinary dish. Give them a little room and they can add wonderful complexity, shining as a main flavor, highlighting a layered harmony, even working as a seasoning.

After you get over the initial acidity, you might notice the herbal notes - key limes have their own harmony going on - a bouquet almost. They are not a one-note fruit.

The key to cooking with them is balance. Because their flavor and nose are so assertive, key limes do not always go well with other flavors. You really need to fine-tune to get a good balance.

There are differences between key limes and the limes we find in stores (commonly called "Tahitian" or "Persian," even though they are not grown in Iran). Key limes (also called Mexican or West Indian limes) are the most common lime found throughout the world; the United States is the exception in preferring the Persian lime.

That's largely because of an accident of history. Key limes were commercially produced in Florida at the turn of the last century, but the crop was wiped out by a hurricane in 1926. When the growers replanted, they chose the Persian lime, which is more disease-resistant and heavier bearing, although key lime trees still can be found in many backyards.

Along with cocktails, probably the most popular way to use key limes is in the eponymous pie. About the only thing everyone agrees on is that it includes key lime juice. Most recipes combine the juice with sweetened condensed milk and egg to form a rich custard. After that, almost anything goes. It can be spooned into either a graham cracker or pastry crust, and topped with either meringue or whipped cream.

Many older recipes do not call for baking the custard; the lime juice alone thickens the mixture over time to "set" the custard.

Cookbook author Rose Levy Beranbaum takes the pie in a different direction, which I like better. She lightens the custard with a bit of Italian meringue. Not only does it improve the texture, it also helps distinguish the flavors on the palate, brightening the lime. The custard is baked in a classic graham cracker crust (baking helps to thicken the texture and firm up the slices) and topped with the remaining meringue, which is baked just long enough to slightly brown the edges.

Incidentally, Beranbaum prefers the Persian lime for the pie. She says the key lime's "bitterness seemed to penetrate the sweetness." I prefer the paunchiness of the key lime.

One quick note here: You cannot bottle fresh flavor. Packaged key lime juice may look easy, but it tastes like the shortcut that it is. Generally made from concentrate and treated for preservation, it lacks punch and often has metallic undertones.

Anyway, it is not hard to find fresh key limes in most Mexican markets. Look for limes that are heavy for their weight, green shading to yellow (yellow signals ripeness and makes for a slightly less tart lime). Store them at cool room temperature because refrigeration can speed decay.

It seems, more often than not, that key limes (and limes in general) appear in sweet recipes, but they can be just as great in savory dishes.

Again, balance is the key. Sweet dishes tend to "tame" lime with sugar or other sweeteners, toning it down and softening it. At the same time, in many savory dishes, the sharp flavor is often contrasted with a spice and/or rich texture, as with guacamole. Lime juice is frequently used in marinades and dressings. Toss some arugula with grapefruit and avocado, then finish the salad with a light dressing of lime juice, honey, and cumin. It's a simple presentation, but the flavors can be stunning - the balance comes from the sweetness of honey, the spice of cumin, and the richness of avocado.

Or try a ceviche. Toss cubed fish in lime juice just until it turns opaque. The acid from the lime firms the fish, much like cooking, and it's balanced by fresh-chopped serrano or jalapeño chili and cilantro. Indeed, lime and chili are frequently paired. Try combining them for a spicy, tangy marinade. It works well with chicken and makes for a particularly fun take on hot wings.

Or try a spicy Thai-inspired marinade: lime juice, chilies, onion, ginger, and garlic. Season with a little soy sauce and toss in a bit of chipotle powder to add a smoky element. Marinate a couple of pounds of chicken wings for a few hours, up to overnight, then fry until golden. Brush the wings with a sweet peanut sauce and finish them in the oven until the sauce cooks to a nice shellac. The combination of flavors is striking: First you get the sweet peanut sauce, followed by the sharp acid and heat from the marinade.

Key limes also go particularly well with coconut. While the lime can be overwhelmingly tart, it works nicely with the rich, sweet flavor of coconut.

Try pairing key lime and coconut in a scone. Substitute coconut milk and a little fresh lime juice for the liquid in a standard recipe, adding some toasted coconut for crunch and a little fresh lime zest to brighten the composition.