"Power! Money! Lust! Sex!" "Power! Money! Lust! Sex!"

Over and over, the throbbing chorus of a dance hit explodes out of a battery of seven-foot-tall (2.1-meter-tall) speakers so powerful that the wood dance floor trembles, earthquake style, with every reverberating bass note. Through a purple haze of smoke and sweat the strobe lights' red glare illuminates the dancing couples: men with mohawks and painted faces, women in vinyl skirts so micro they serve no functional purpose. It's 4:45 a.m. at the popular London club Egg, and a few dancers have collapsed on the sofas or taken refuge at the bar. But after a long night of liquor, drugs, tobacco, and earthshaking noise, most are still vigorously, and happily, strutting their stuff across that trembling wood floor. How do they do it?

"Actually, we usually see a revival about half four or so in the morning," says Egg night manager Simon Patrick. "That's when we get the real rush at the bar for Red Bull. And the kids say, 'I've had eight Red Bulls—I'm flying!' They'll dance right round the clock. At seven in the morning we have trouble getting them out the door."

"It's like putting your whole system on fast-forward," Lee Murphy shouts above the din as he glides across the floor with four-inch-high (10-centimeter-high) soles on his dancing shoes, a gold ring in his chin, and a slender silver and blue can of Red Bull energy drink in each hand. "By four or five in the morning you're totally blotto," the 29-year-old London nurse explains. "That's where the Red Bull comes in. I drink these two tins, it's like drinking a pint of speed."

For Lee Murphy and other habitués of the all-night club scene around the world—not to mention a legion of marathon runners, mountain bikers, fighter pilots, college crammers, and late-night truckers hoping to cover another hundred miles (160 kilometers) before turning in—the canned concoctions marketed as energy drinks represent a fizzy new manifestation of one of mankind's oldest stimulants: caffeine. The active ingredient in the hugely successful Austrian product Red Bull is a solid jolt of caffeine, blended with a handful of other ingredients. One 8.3-ounce (0.25-liter) can has two to three times the amount of caffeine as a 12-ounce (0.35-liter) can of soda.

"The kids in the clubs, they think they've happened upon this great new invention," says Neil Stanley, director of sleep research at the Human Psychopharmacology Research Unit at Britain's University of Surrey. "But we've known for centuries that caffeinated drinks work. They get you out of an energy slump and make you more alert. Really all they've found is a new kind of caffeine delivery system."

The dual power to counter physical fatigue and increase alertness is part of the reason caffeine ranks as the world's most popular mood-altering drug, eclipsing the likes of nicotine and alcohol. The drug is encountered not just at the soda fountain or the espresso bar but also in diet pills and pain relievers. It is the only habit-forming psychoactive drug we routinely serve to our children (in all those sodas and chocolate bars). In fact, most babies in the developed world enter the universe with traces of caffeine in their bodies, a transfer through the umbilical cord from the mother's latte or Snapple.

Caffeine's pervasiveness is a cause for concern among some scientists and public health advocates, but that hasn't dampened its popularity. Sales of Red Bull and copycat energy drinks with names like Red Devil, Roaring Lion, RockStar, SoBe Adrenaline Rush, Go Fast, and Whoop Ass are booming. Meanwhile new coffee shops are opening so fast all over the world that even the most dedicated devotee of the triple-shot, no-foam, double-caramel, skinny macchiato can't keep track. Every working day, Starbucks opens four new outlets somewhere on the planet and hires 200 new employees. There's a joke in many cities that Starbucks is going to open a new store in the parking lot of the local Starbucks, but this is not true. Yet.

It was less than 200 years ago that people first figured out that the buzz they got from coffee and tea was the same buzz, produced by the same chemical agent. An alkaloid that occurs naturally in the leaves, seeds, and fruit of tea, coffee, cacao, kola trees, and more than 60 other plants, this ancient wonder drug had been prescribed for human use as far back as the sixth century B.C., when the great spiritual leader Lao-tzu is said to have recommended tea as an elixir for disciples of his new religion, Taoism.

But it wasn't until 1820, after coffee shops had proliferated in western Europe, that a new breed of scientist began to wonder what it was that made this drink so popular. The German chemist Friedlieb Ferdinand Runge first isolated the drug in the coffee bean. The newly discovered substance was dubbed "caffeine," meaning something found in coffee. Then, in 1838 chemists discerned that the effective ingredient in tea was the same substance as Runge's caffeine. Before the end of the century the same drug would be found in kola nuts and cacao.

It's hardly a coincidence that coffee and tea caught on in Europe just as the first factories were ushering in the industrial revolution. The widespread use of caffeinated drinks—replacing the ubiquitous beer—facilitated the great transformation of human economic endeavor from the farm to the factory. Boiling water to make coffee or tea helped decrease the incidence of disease among workers in crowded cities. And the caffeine in their systems kept them from falling asleep over the machinery. In a sense, caffeine is the drug that made the modern world possible. And the more modern our world gets, the more we seem to need it. Without that useful jolt of coffee—or Diet Coke or Red Bull—to get us out of bed and back to work, the 24-hour society of the developed world couldn't exist.

"For most of human existence, your pattern of sleeping and wakefulness was basically a matter of the sun and the season," explains Charles Czeisler, a neuroscientist and sleep expert at Harvard Medical School. "When the nature of work changed from a schedule built around the sun to an indoor job timed by a clock, humans had to adapt. The widespread use of caffeinated food and drink—in combination with the invention of electric light—allowed people to cope with a work schedule set by the clock, not by daylight or the natural sleep cycle."

Czeisler, who rarely consumes any caffeine, is a bundle of wide-awake energy in his white lab coat, racing around his lab at Boston's Brigham and Women's Hospital, grabbing journal articles from the shelves and digging through charts to find the key data points. "Caffeine is what's called a wake-promoting therapeutic," he says.

Scientists have developed various theories to explain caffeine's "wake-promoting" power. The consensus today focuses on the drug's interference with adenosine, a chemical in the body that acts as a natural sleeping pill. Caffeine blocks the hypnotic effect of adenosine and keeps us from falling asleep. Since caffeine has also been shown to enhance mood and increase alertness in moderate amounts, it's a potent potion for students and scholars stuck in the lab at three in the morning. Paul Erdős, the Hungarian mathematician who often worked his equations around the clock, is known for saying that "a mathematician is a machine for turning coffee into theorems."

Caffeine's ability to murder sleep also makes it a drug of choice for long-distance travelers. There are as many different jet-lag remedies as there are seats on a trans-Pacific flight. But one approach, outlined in The Caffeine Advantage by Bennett Alan Weinberg and Bonnie K. Bealer, involves abstaining from caffeine for several days before traveling, then dosing yourself with small amounts of coffee or tea on the day you arrive to stay alert—preferably out in the sunshine—until your regular bedtime in your destination. (During weeks of global travel for this article, it worked for me.)

"Caffeine helps people try to wrest control away from the human circadian rhythm that is hardwired in all of us," says Czeisler. But then a shadow crosses the doctor's sunny face, and his tone changes sharply. "On the other hand," he says solemnly, "there is a heavy, heavy price that has been paid for all this extra wakefulness." Without adequate sleep—the conventional eight hours out of each 24 is about right—the human body will not function at its best, physically, mentally, or emotionally, the doctor says. "As a society, we are tremendously sleep deprived."

In fact, the professor goes on, there is a sort of catch-22 at the heart of the modern craving for caffeine. "The principal reason that caffeine is used around the world is to promote wakefulness," Czeisler says. "But the principal reason that people need that crutch is inadequate sleep. Think about that: We use caffeine to make up for a sleep deficit that is largely the result of using caffeine."

Dietrich Mateschitz isn't losing sleep over how much caffeine he consumes. A big, friendly man with a big, friendly smile that beams out from his stubble of white beard, the Austrian marketing whiz describes himself as "comfortable with risk," whether he's climbing a rocky cliff, helicopter skiing, mountain hiking an impossibly steep trail in the Alps—or doing business. Mateschitz ought to be comfortable with risk, because the biggest chance he ever took paid off in spectacular fashion, placing a whole new product on supermarket shelves, spawning hundreds of competitors, and making himself a billionaire, all within 15 years.

In the 1980s Mateschitz was working for Blendax, a German cosmetics company, marketing skin care products and toothpaste in East Asia. His regular overnight flights from Frankfurt to Tokyo and Beijing inevitably resulted in jet lag, which Mateschitz came to despise. He was a salesman, after all; he needed to be at the peak of energy to do his job right. But the long flights left him drained and worn. He began to notice that taxi drivers in most Asian cities were regularly sipping from small bottles of tonic. After one exhausting flight to Bangkok, he asked the cab driver to share the drink.

Eureka! "Jet lag was gone," he recalls. "Suddenly, I felt so awake." Relating the story nearly two decades later, Mateschitz still remembers the sheer excitement of that moment of discovery. "I found these drinks all over Asia, and there were huge markets for them. I started thinking: Why doesn't the West have this product?"

The West, of course, already had the key ingredient of those Asian mixtures: caffeine. The drink that worked so well for Dietrich Mateschitz, a Thai tonic named Krating Daeng (that is, Red Bull), was a blend of caffeine, an amino acid called taurine, and a carbohydrate, glucuronolactone. The Austrian quit his toothpaste-selling job and invested his life savings in a license to sell Krating Daeng in the West. After tinkering somewhat with the flavoring and the packaging—and adding carbonation—he launched the beverage in Europe in the late 1980s.

At first, stores didn't know what to do with an energy drink. There was no such product, and thus no market for it. Mateschitz solved that problem with a brilliant marketing campaign. "You don't drink Red Bull. You use it," the ads proclaimed. "You've got better things to do than sleep." "Red Bull gives you wings."

Red Bull began organizing extreme sporting events, ranging from kitesurfing, streetluge, and paragliding to its Flugtag championships (that is, human-powered flying machines) and its own Seifenkistenrennen, or Soap Box Derby. The target market was the educated, vigorous, and well-paid European youth culture—people who spent long days on the trading floor and the running track and long nights at downtown clubs, dancing and drinking until dawn.

By the turn of the century, the hottest new cocktail among Europe's clubbing set was the Vodka Bull, Red Bull mixed with vodka. (You can also buy a Bullgarita, which is Red Bull with tequila, a Chambull, which is Red Bull with champagne, or a Bullmeister, which is Red Bull with Jägermeister.) "Red Bull rocks, right around the clock," the company said in its advertising, including the helpful assurance that "Adding alcohol does not change Red Bull's properties."

Red Bull arrived in the United States in 1997, promoting a series of extreme sporting events and hiring "social superstars" on college campuses to serve as Red Bull brand managers. Today the product is in more than a hundred countries, selling close to two billion cans a year.

The home office of Red Bull, in a breathtaking corner of the Austrian Alps beside a blue jewel of a mountain lake called the Fuschlsee, feels more like an upscale beach club than the world headquarters of a multibillion-dollar corporation. Mateschitz asked the architect to create the building in the form of two erupting volcanoes to reflect the product's explosive sales growth. Young staffers in tank tops and denim fill the company parking lot with their mountain bikes; a large black dog sleeps under the 20-foot-high (6.1-meter-high) palm trees in the lobby outside the CEO's office. Herr Mateschitz, now 60, follows the code, wearing jeans and loafers to work (no socks) and joining in beach Volleyball games on the lakefront with his junior executives.

Mateschitz modestly plays down his own role in the success of Red Bull and gives all the credit to the "formula." "In marketing, you differentiate from existing products," he says. "Now coffee offers the caffeine, but in a bitter form, not cold and refreshing. Other soft drinks are refreshing and thirst quenching, but they offer no benefits. Pleasure was a good thing to market, but we saw that there was a place also in that market for efficacy, for a pleasurable drink that serves a function. This is the niche; this is Red Bull."

The idea of giving a soft drink a "function" by adding in hefty doses of a habit-forming drug makes some people more than a little nervous. France and Denmark have banned energy drinks like Red Bull altogether, citing health concerns about the elevated caffeine level, as well as the addition of other supplements. Initially, even cans of Red Bull sold in its home country, Austria, carried the warning Nicht mit Alkohol mischen—Don't mix with alcohol.

Alarms were raised in Ireland after an 18-year-old basketball player drank several cans of Red Bull before a game—and then collapsed and died on the court. A coroner's inquest was inconclusive about whether Red Bull had contributed to this sudden death. But the unexplained collapse of an athletic young man prompted the government in Dublin to establish a Stimulant Drinks Committee to study the impact of energy drinks on Ireland's public health.

"The first thing I noticed, when the committee was meeting, was how much coffee they drank," says Martin Higgins, the energetic chief executive of Ireland's food safety promotion board, which supervised the study. "I guess we all have to get our stimulants one way or another." Although the committee looked at all the ingredients of Red Bull and similar products, it concluded that caffeine was the major attraction. "It wasn't so much energy or physical strength that people were buying," Higgins says. "It was that caffeine buzz, particularly in the nightclub setting. And it was the caffeine that prompted the most concern from the committee."

In the end, the Stimulant Drinks Committee found no serious risk from consumption of caffeinated energy drinks—at moderate levels. The group recommended warning labels saying the drinks are unsuitable for children, pregnant women, and people sensitive to caffeine, as well as public health reminders that caffeinated energy drinks should not be consumed for rehydrating purposes during sports or exercise.

Last year the European Union, guided in part by the Irish study, began requiring packaged drinks with more than 150 milligrams of caffeine per liter to be labeled "high caffeine content" drinks. By that standard, Red Bull and most of its competitors are high-caffeine beverages—so is any cup of coffee, for that matter—but most colas and other soft drinks are not. The labeling requirement applies in all 25 EU nations. Australia and New Zealand have also adopted warning requirements. The United States has no such rule, but many canned energy drinks sold in the U.S. carry warnings anyway.

One member of Ireland's Stimulant Drinks Committee who was not at all satisfied with its proceedings—indeed, he decided to withdraw from the study group—is Jack James, a psychologist who believes there is little to be gained from labeling some drinks high caffeine. He says that such a label implies consumers are perfectly safe in drinking beverages with lower levels of caffeine, a conclusion he says isn't supported by the evidence. While consumers around the world continue their intake of the drug year after year, James sits in his spartan office at the National University of Ireland's Galway campus, documenting the reasons they should stop. A colleague once dubbed him a caffeine crusader. An Australian native with curly hair, wire-rim glasses, and a steely determination, James sips at a glass of tepid water over the course of a four-hour interview. Previously a daily consumer of caffeine, he's mostly sworn off the stuff for years. "People at the scientific meetings say to me, 'Hey, Jack, want a coffee?'"

James has criticized research reports funded by the soft drink and coffee industries, which he says portray caffeine as a benign substance while ignoring evidence of its potential adverse effects. His own research papers warn that caffeine is a psychoactive drug that raises blood pressure and thus increases the risk of heart disease.

But Jack James's view is out of sync with most public health pronouncements about caffeine. While the coffee and soft drink industries do finance some laboratory work on caffeine, there are also many independent investigators. And the consensus view seems to be that the world's most popular drug is not dangerous at moderate levels of consumption—up to 300 milligrams (one to two small-12-ounce-take-out (small-0.35-liter-take-out) cups of coffee or six to eight cans of soda a day).

Caffeine is still a drug, though, which may explain why it makes people worry. Over the years population studies have shown that people who consume caffeine have higher rates of kidney and bladder cancer, fibrocystic breast disease, pancreatic cancer, and osteoporosis. Yet such findings cannot prove that caffeine caused the disease. All that can be studied are short-term effects.

Like other drugs, caffeine does have a definite impact on mental and physical functions. Repeated studies have shown that caffeine is analeptic (it stimulates the central nervous system) and ergogenic (it improves physical performance). It is also a diuretic, though recent studies show that it is not dehydrating in moderate amounts, even in athletes, as has been widely believed. Caffeinated drinks do increase urine output, but only about the same as water. Caffeine boosts blood pressure, too, but this effect is temporary. And while some studies have shown that caffeine increases calcium loss, any effect is so small that it could be eliminated with as little as two tablespoons of milk a day.

Indeed much of the research suggests that caffeine may have benefits for human health. Studies have shown it can help relieve pain, thwart migraine headaches, reduce asthma symptoms, and elevate mood. As a mental stimulant, it increases alertness, cognition, and reaction speed; because it combats fatigue, it improves performance on vigilance tasks like driving, flying, solving simple math problems, and data entry.

And despite its nearly universal use, caffeine has rarely been abused. "With caffeine, overuse tends to stop itself," says Jack Bergman, a behavioral pharmacologist in the department of psychiatry at Harvard Medical School. "You get jittery and uncomfortable, and you don't want to continue." The point at which an individual reaches that jittery stage varies greatly. Some people seem to be genetically more susceptible to caffeine's effects and may have increased anxiety after consuming even small amounts. In a minority of people, doses of 300 milligrams or more may prompt an increase in tension, anxiety, even panic attacks, which may account for why studies show that nervous people generally have lower caffeine consumption.

As for caffeine use among children, it's clear that their lower body weight means they should consume less than adults. Ireland's Stimulant Drinks Committee report advised that consumption of high-caffeine beverages should be discouraged in children to prevent possible increases in anxiety or nervousness. But there's no conclusive evidence about whether caffeine is harmful to children in small amounts. A report from the Australia New Zealand Food Authority concluded that children appear to metabolize caffeine more quickly, and that there was no reason to suspect that they are more sensitive to its effects—good or bad—than adults.

Even for pregnant women, a population the Food and Drug Administration advises to avoid caffeine if possible, risks appear to be small, as long as daily intake is kept to moderate levels. Michael Bracken, a perinatal epidemiologist at the Yale School of Public Health, has tracked the habits of thousands of expectant mothers over the past two decades. "Based on current evidence, we can safely say to a pregnant woman, if you're under 300 milligrams of caffeine per day—that's about one to two cups of coffee—you're not doing anything harmful to the child."

After decades of testing, caffeine remains on the FDA's list of food additives "generally recognized as safe." "Looking at all the studies of caffeine, it is very hard to argue that moderate consumption is bad for you," says Bergman. "The behavioral effects are real, but mild. It undoubtedly produces some physical dependence. I get up in the morning and usually have a couple cups of coffee. But when I don't, the withdrawal symptoms aren't severe."

Some caffeine users might argue with Bergman: A day or so without caffeine can cause headaches, irritability, a lack of energy, and, of course, sleepiness. But compared with giving up cocaine or heroin, getting over caffeine is short and easy. Withdrawal symptoms tend to disappear in two to four days, though they can last up to a week or more. Still, the desire to avoid withdrawal pangs may explain why billions of humans so eagerly consume caffeine every day. The person who says, "I'm a monster until that first cup of coffee in the morning," is describing a mild form of addiction.

In fact, Jack James contends that the widespread physical dependence on caffeine may have skewed research findings, exaggerating caffeine's mood-boosting effects. If scientists compare two groups of subjects—some who have been given caffeine and others who have not—any improvement in mood or performance in the caffeinated group could be simply a relief from withdrawal symptoms. "It may be that we are all on one of those endless cycles," agrees Derk-Jan Dijk, a physiologist at the University of Surrey's sleep research center. "You take caffeine, and you are more alert. Then the next morning, the effect has worn off and you need more of the drug to restore the alertness. But maybe we could step off the cycle. For those of us who work during the day, we might do just as well without caffeine."

On the other hand, that coffee ritual in the morning, maybe with your doughnut, is a normal part of life that we enjoy. It's calming. It helps order the day. And all that can be useful for anybody. Over the centuries humans have created countless rituals to accompany consumption of their favorite drug. Often, the ritual has grown to transcend the beverage. In Japan's austerely elegant chanoyu, or tea ceremony, the simple surroundings of the tearoom, the soft rustle of kimono across tatami floor, the spare beauty of a hand-molded brown cup, matter as much as the tea itself.

The British have turned their afternoon ritual into a pageant of pomp and luxury. In the glittering splendor of London's Fortnum & Mason food emporium, afternoon tea is served amid green marble pillars and huge floral sprays, in fine china cups of gold and green. Obsequious waiters serve finger sandwiches, scones with clotted cream, and tropical fruit tarts with the Earl Grey or Lapsang Souchong. A pianist in the center of the room plays "On the Sunny Side of the Street"—just right, because you do indeed feel rich as Rockefeller, at least until the teapot runs dry and the check ($44!) arrives.

Americans, true to form, have engineered a rather more casual set of caffeinated rituals: a cruller and coffee at the local Dunkin' Donuts, or instant with powdered creamer and Sweet'n Low at the desk. In the past decade or so, however, America's morning rite of caffeine consumption has moved decidedly upscale. A flood of new coffee shops has turned the 75-cent cup of perked joe, refills free, into a six-dollar extravaganza brewed and blended expressly for each customer by a personal barista.

"We have built a whole new ritual of coffee in this country," says Howard Schultz, the man who invented Starbucks. In two decades Schultz turned a single espresso bar in a coffee shop at the corner of Fourth and Spring in Seattle into a Fortune 500 company, building a global icon so familiar that Playboy has done a feature on the "Women of Starbucks." A five-cup-a-day coffee drinker himself, the 51-year-old Schultz is a picture of intensity as he prowls his office and recalls how it all began.

Schultz was a coffee bean salesman for a Seattle coffee bean store named Starbucks—after the first mate in Melville's Moby Dick—when he visited Milan in 1983 and fell in love with the ambience of that great Italian institution, the espresso bar. "It was about excellent coffee, but it was more than that," he says in passionate tones. "It was about conversation. About community. About human connection. And fine coffee was the link. I thought, You know, we could do this in Seattle."

On a drizzly (what else?) Seattle morning in April 1984, Schultz set up a tiny espresso bar in the rear corner of the coffee bean store, offering mysterious beverages like caffe latte that the likes of Dunkin' Donuts had never dreamed of. Within days there were long lines on the sidewalk outside, and Howard Schultz never looked back. He soon left the company and opened his own espresso bar, called Il Giornale, or The Daily. Two years later he bought out his former employer, and now there are more than 8,500 Starbucks around the world, with another 1,500 scheduled to open this year.

Schultz doesn't like to emphasize the role caffeine may play in his company's success: "I don't think it's the caffeine. I think the ritual, the romance of the thing, is really more important."

But the caffeine is there. A few miles down the interstate from Schultz's office, at the Starbucks roasting plant in Kent, Washington, supervisor Tom Walters knows that firsthand. "I've been asked not to make the connection between coffee and caffeine," Walters says as he strolls past mountains of 70-kilogram (154-pound) burlap sacks holding fresh-picked beans from Colombia, Costa Rica, Nicaragua, Indonesia. "But we see a hell of a lot of caffeine around here. When you roast the beans, the caffeine forms a kind of fuzz on the roaster. So when we're too busy to get a coffee break, some people just run a finger down the casing of the roaster and lick it, and get their jolt that way."

Getting that jolt, of course, is why many of the most popular beverages on Earth—coffee, cola, tea—just happen to contain caffeine. Whether it's a graduate student downing mocha in the lab or a monk sipping green tea while chanting in the temple, mankind's favorite stimulant is at work every day, all over the world.