TEQUILA IS MADE from a single species of agave, Agave tequilana Weber, a spiky-leaf succulent related to the lily that takes between seven and ten years to mature and whose large heart, when cooked, tastes like tangy apricot.

Tequila's country cousins-sotol, raicilla, bacanora, worm-drowning mezcal-are made in different areas from different species of agave. Real tequila comes only from Jalisco-a Mexican state about the size of South Carolina-and a couple of neighboring hamlets.

The best tequilas are the sipping tequilas made purely from agave, like Cuervo Tradicional. Mexicans call this cien por ciento ("one hundred percent"), as opposed to mixto or "tequila tequila" like Cuervo Gold, which is only 51 percent agave, the minimum allowed by law. The rest is stuff like sugar, caramel color, and other additives.

Cien por ciento comes in four grades based on age. Blanco is bottled almost straight from the distillation tank. Reposado ("rested") sits at least two months in wooden barrels to soften the flavor. Añejo, or "aged," tequila rests for at least a year. Since 2006, there's been a grade called extra añejo, aged three years or more. Blancos are often used for margaritas, and the others for sipping, but all can be excellent straight or mixed.

Legend has it that primitive tequila was discovered by an ancient tribesman who stumbled on an agave heart that was flash-fermented by a lightning strike. (Dude!) However it started, tequila-making isn't very complex. Cook the agave to release its sugar, add yeast to turn the sugar to alcohol, separate the alcohol through distillation, and voilà: basic tequila. Many locals still whip up home brew with this rudimentary technique.

Of course, the process has grown more sophisticated, thanks in large part to the 100-plus-year-old tequila superpowers: Cuervo, Sauza, and Herradura. Patrón, a top-ten manufacturer with a plant in Jalisco, was founded in 1989 by two Las Vegas-based Americans and is now the most popular sipping tequila in the world. The success of this young yanqui upstart has inspired resentment among its Mexican competitors, but there's no denying that it has introduced millions to the joys of sipping. Patrón sold 100,000 cases in 2000; 1.6 million last year.

These days, rare is the big city without at least one high-class cantina boasting a mirrored wall of blown-glass bottles. A certified-organic tequila, 4 Copas, recently hit the market. And in 2006, a $225,000 bottle of tequila, called Pasión Azteca, sold in Mexico City, setting the record for the most expensive bottle of liquor ever sold. This was a publicity stunt in which the makers dipped a bottle in "white-gold and platinum." In the real world, serious tequila is an easier get, costing anywhere from $30 to $300.