There is a reason why life is built of cells, and why most cells are too small to see without a microscope. It’s easy in a small space to keep critical components squeezed together and close at hand, the better for the right enzymes to encounter the right substrates in a timely fashion and a million tiny bonfires to burn. “Cells are not like an aquarium where a fish swims by now and again,” said Dr. Bassler. “They’re jam-packed inside. They’re teeming with stuff. They’re like a house filled with necessary clutter, or New York City, or a Thanksgiving table loaded with so many dishes you don’t know where you might put another plate.”

Much of the cell’s interior is taken up by the cytoplasm, which, as several biologists have gleefully observed, pretty much has the texture of snot. The appearance of random ooze, however, is deceptive. “There’s a beautiful architecture” to the cytoplasm, Dr. Bassler said. “Everything is in the right place and bumping around, and the membrane holds them together so they can’t get away from each other.”

When the Venter team inserted the synthetic version of the Mycoplasma mycoides genome into the cellular housing of the Mycoplasma capricolum bacterium, the newcomer took full advantage of the resident cytoplasmic wares. It used the thousands of little biodevices called ribosomes to stitch together amino acids into new proteins. It relied on complex molecular assemblages to maintain its DNA in working order and to duplicate that DNA when it was time to divide. It thanked its lucky base pairs that a greasy lipid cell membrane and stiffer bacterial wall not only kept the inside appropriately, bioactively dense, but also kept the outside appropriately out, for an exposed cytoplasm would soon be scavenged for parts, most likely by a neighboring microbe.

Considered together, the modern cell is dauntingly complex, which is why most researchers in the youngish field of synthetic biology address only one or two pieces of it at a time. Last year, George Church of Harvard Medical School and his colleagues reported that they had created an artificial ribosome. James J. Collins, the co-director of the Center for Biodynamics at Boston University, is working on a synthetic DNA toggle switch, to flip genes on and off at will.

In Denmark, Dr. Rasmussen is seeking to design the most stripped-down minimalist suggestion of a functioning cell. As he sees it, there are three basic capacities that a living cell must possess. It must have a means of channeling free energy in the environment to meet its demands: that is, it must have some form of metabolism. It must have an enclosure: a cell membrane. And it must have the informational wherewithal to reproduce itself: a genome. Dr. Rasmussen and his co-workers have devised reasonable if crude facsimiles of the three cellular non-negotiables, and they’ve managed to merge two of them together in any given experiment — and in one case even all three of them. The goal of contriving a self-replicating and autonomously metabolizing protocell, however, continues to elude them. “We have the instruments,” he said, “but it doesn’t sound like an orchestra yet.”

Just pick up your baton, hum a few bars, and give it three billion years.