Editor's Note: This is the second in a series of six features on the science of food, running daily from March 30 through April 6, 2009.

UTRECHT, the Netherlands—Just down the hall from a frozen vat of pig semen on the über-modern campus of Utrecht University here, Bernard Roelen pulls out a clear, rectangular flask from his precision incubator. The molecular biologist is careful not to leave the door open too long, as slight fluctuations in air temperature, humidity or carbon dioxide are enough to upset the precious piece of pork growing inside. If he succeeds in turning these embryonic stem cells into a slice of sausage, Roelen could make carnivory socially respectable even to the most ardent vegetarian. "There is a point that the Earth is not big enough to have all the animals and the fields to feed all the animals," he says, "You have to think ahead."

According to ecologist David Pimentel of Cornell University's College of Agriculture and Life Sciences, some 12,000 gallons (45,500 liters) of water are needed to produce every pound (0.45 kilogram) of beef, compared with just 60 gallons (225 liters) for a pound of potatoes. Beef requires 27 times more energy to produce than plant protein. The methane burps of 56 billion farm animals (as enumerated by the United Nations Food and Agriculture Organization) are a significant contributor to climate change, and their nutrient-rich manure pollutes waterways. Raised under sterile conditions, lab-grown meat could reduce food-borne illnesses such as Escherichia coli and salmonella. And, for some animal rights activists, meat may no longer be "murder."

Slide Show: Growing Meat inside a Test Tube

In a prescient essay from 1932, Winston Churchill wrote, "Fifty years hence, we shall escape the absurdity of growing a whole chicken in order to eat the breast or wing by growing these parts separately under a suitable medium." Although Roelen has a lot of work ahead of him to fulfill Churchill's prediction, the dream got a boost last April with the first In Vitro Meat Symposium in Norway and with the announcement by the People for the Ethical Treatment of Animals (PETA) of a $1-million prize for a commercially viable in vitro chicken product. When I ask Roelen if he's competing for the PETA prize, he chuckles, "We don't work on chicken."

In any case, with its four-year deadline, the PETA prize is nothing more than a publicity ploy, some skeptics insist. After all, in the past three decades, scientists have only succeeded in deriving embryonic stem cell lines from two animal species: the mouse in 1981 and the human in 1998. "Saying you have meat grown in a lab would already be a big step,” Roelen points out. "Saying you have meat grown from a lab and it's mouse tissue—that's asking too much." Presumably, the same goes for human tissue.

The Dutch In Vitro Meat project is the brainchild of businessman Willem van Eelen, now in his 80s, who nearly starved to death in a Japanese prison camp during World War II and came to believe that in vitromeat could solve world hunger. He later took classes in biology and consulted with researchers and companies over 25 years, culminating in a series of patents on in vitro meat production, which he filed in the late 1990s. In 2005 the Dutch government granted three universities and a Dutch meat processor owned by Smithfield Foods two million euros over four years to develop Eelen's idea.

But the flask in Roelen's hands today is just filled with a thin layer of fluid, the color of red Kool-Aid but slightly more viscous. Floating within this growth medium, but not quite visible to the naked eye, is the protomeat. "I get all these phone calls and e-mails from people saying, 'Can I taste something?'" Roelen recounts. "You can scrape the cells on the surface, and then you may have this snotty substance, but that would not be so good." I decline his offer of a taste, and he places the gooey mass under a microscope and adjusts the focus knob. Suddenly, I see that the entire wall is speckled with the elusive embryonic stem cells that have the potential to transform into any part of the pig's body—bones, blood, brains or, for Roelen's work, muscle.

The process begins, ironically, with a nearby slaughterhouse, from which Roelen has retrieved pig ovaries. The eggs mature in vitro and are then fertilized with pig semen, transforming them into embryos. Placed in a nutrient bath, the embryonic cells divide and grow, changing along the way. Some are just motionless blobs, but others pulse to an eerie rhythm, having spontaneously transformed into heart muscle despite Roelen's desire to keep them in their undifferentiated state.

"You can see the cells have started to align, but they have not fused yet," Roelen says. "You want that process to be as efficient as possible." In the future, meat-growers may forgo the dish and culture stem cells on an edible, three-dimensional scaffold, and, with the right chemical signal, they would transform into sumptuous fibers of skeletal muscle protein. Roelen's colleagues at the Eindhoven University of Technology are even working on ways to "exercise" tissue through electrical stimulation to give them a more natural texture.

Unfortunately, Roelen's cultures only survive a few months before they sputter, failing to reproduce because of genetic problems—their chromosomes become deformed or cells end up with too many copies. His group also works with adult stem cells extracted from skeletal muscle—a direct approach for in vitro meat.

Tor Erling Lea, a biologist at the Norwegian University of Life Sciences in Aas who is also pursuing test-tube meat, acknowledges that Roelen is the leader in the field, but he's not impressed with either the embryonic or adult approach so far. "I think what they have achieved is what we could expect to achieve," he says. At last year's In Vitro Meat Symposium, Lea presented his preliminary work on stem cells derived from the umbilical cords of pigs. They are easier to work with, and he calculates that it's possible to culture up to 10,000 pounds (4,500 kilograms) at a time, but so far he has only produced fat and cartilage.

Even if Roelen's team succeeds in culturing enough muscle cells for a bacon substitute, the team still faces with the problem of what to feed their disembodied animal. The red Kool-Aid–colored medium has just about everything a growing muscle needs; the only problem is that it's derived from cow blood. Vegetarians certainly aren't going to stomach bovine serum albumin. Alternatives exist, but they are far too costly for food production. Molecular microbiologist Klaas Hellingwerf of the University of Amsterdam believes that a suitable substitute lies in a medium based on yeast or algae. He has done preliminary experiments to get genetically modified algae to produce a growth factor that will encourage Roelen's stem cells to multiply.

Before I leave, I can't help but ask Roelen if he would consider eating his lab-grown meat. "Why not?" he responds, noting that people have no problem scarfing down imitation cheese and other processed foods. He has a point, assuming he can get his meat past the snot phase.