cientists at the American Museum of Natural History are building a 21st century version of Noah's Ark. Except this time, instead of two by two, the animals will go in little bits and pieces, deep frozen.

The tissue specimens — from whole insects to leeches to small pieces of whales — will be a treasure trove for researchers using genetic techniques to study wildlife, and perhaps one day will become the source material for creating clones of endangered or extinct animals.

All of this is out of view of museum visitors.

In a new 2,000-square-foot laboratory in the museum's basement, nine stainless steel vats will each eventually hold up to 70,000 tissue samples, all immersed in liquid nitrogen. The museum started the flow of liquid nitrogen to two vats a couple of weeks ago and plans to put in the first tissue samples this month.

"We want to make this the central repository for nonhuman comparative genomics," said Dr. Michael J. Novacek, the museum's senior vice president and provost of science. "This is the first wholly new kind of collection we've established here in a few decades."

Over the past couple of decades, biology has shifted from descriptions of physical appearances to examinations of genes. The genetic studies have refined and redrawn many of the family relationships of different creatures.

Part of the $1 million financing for the new laboratory came from NASA. "They view a collection like this as a source of information on the evolution of life on this planet," Dr. Novacek said, "and thus a potential source for insight on the nature and evolution of life if they encounter it elsewhere."

The American Museum of Natural History is not the first to collect and freeze. For example, the Museum of Natural Science at Louisiana State University, known for its specimens of exotic birds, has been doing that for more than two decades.

When Dr. Mark Haffner, now the museum's director, arrived at Louisiana State in the late 1970's, biologists there typically skinned the specimens, stuffed them and mounted them in the collections. "A lot of us joked they were saving the wrapper, throwing away the gift," he recalled. "They've lost the DNA, the organs, a lot of the information."

At Dr. Haffner's urging, the museum's biologists started taking canisters of liquid nitrogen with them. When collecting a specimen, they preserved some of the innards in the liquid nitrogen. Today, the Louisiana museum houses frozen tissues from 37,000 birds, 15,000 reptiles and amphibians and a smattering of mammals and fish.

One family tree sorted out with help of the Louisiana collection is the relationship of several closely related types of birds: chickadees, titmice, great tits and blue tits.

Chickadees and titmice store seeds for later eating; great tits and blue tits do not. But all are similar in appearance, prompting this question: Did chickadees and titmice independently evolve their seed-storing behavior — so-called parallel evolution — or are titmice more closely related to chickadees?

"The only way you can determine that is phylogenetics," said Dr. Frederick Sheldon, curator of the Louisiana collection. Comparison of the birds' DNA showed that all chickadees and titmice share a common ancestor and that the great tits and blue tits are more distant relatives.

The stored tissues also help answer questions that no one could have thought of when the tissues were first frozen. Recently, researchers studying the deadly hantavirus, which has been spread through the Southwest through the droppings of rodents, requested tissue samples from rats and mice collected in the 1970's and 1980's. "They can see whether the viruses are in the tissues," Dr. Sheldon said.

That could tell how the virus has spread and mutated over the years.

While it will not be the first, the American Museum of Natural History hopes to build the largest, most comprehensive frozen tissue collection, with up to one million samples covering the major groups of animals. Some of the samples will probably come from the Wildlife Conservation Society, which runs the Bronx Zoo. When an animal died at the zoo, scientists at the society saved part of it for future research.

"Typically, they're organ tissue — liver, spleen, kidney — usually a gram or two representing an individual," said Dr. George Amato, director of the society's science resource center. "By banking it, you're preserving your opportunity to do the research even before the research question comes up."

At the American Museum of Natural History, frozen animals — mostly insects — are already scattered in freezers throughout the building. On a recent afternoon, Dr. Robert DeSalle, associate curator of entomology, lifted the lid of an eight-foot-wide freezer on the fifth floor. A piece of paper taped to the freezer lid lists which boxes inside belong to which researchers, but gives no hints of what's inside. "This is kind of embarrassing," said Dr. DeSalle as he rummaged through boxes and plastic bags inside. "I think there's some cool stuff over here."

From one cardboard box, he pulled out a matchbox containing a large spider collected by a museum scientist. Another box contained shed snake skins.

In contrast to the makeshift storage upstairs, the new lab downstairs is efficient and organized. Instead of matchboxes, tissues are stored in identical glass vials, each large enough to hold just 1/20th an ounce of water. (The spider in the matchbox is too large, but "we'll make it fit," Dr. DeSalle said.)

A computer database tracks each bar-coded vial, including where the specimen was collected, who collected it, even how many times it has been thawed and refrozen. Each defrosting degrades the tissue a little; each genetics experiment requires destroying some of the sample.

Among the first creatures to be put into the vats will be Dr. Mark E. Siddall's leeches, now stored in another freezer at the museum. The anticoagulants in the leeches, which prevent clotting as they imbibe blood from their hosts, have potential uses for pharmaceuticals, but the European variety has become threatened in much of its habitat. "It is heavily, heavily exploited," said Dr. Siddall, an assistant curator at the museum.

Through genetic studies, Dr. Siddall has found close relatives of the European variety that might produce similar anticoagulants. Interestingly, one close relative turned out to be a species that no longer sucks blood, but which still produces the anticoagulant. "No one would have thought to look at them because they don't feed on blood," he said.

The museum does not have any plans to try to clone any animals from the frozen tissues. Dr. Novacek calls such speculation "overwrought." Even if possible, cloning does not preserve the natural habitats needed for animals to survive in the wild. "It's a very artificial approach for saving species," he said.

Scientists at a biotechnology company in Massachusetts earlier this year cloned a gaur, an endangered oxlike animal from Asia, using tissue frozen for eight years at the San Diego Zoo. The baby bull gaur died two days later from an infection unrelated to the cloning.

In any case, Dr. Amato of the Wildlife Conservation Society also points out that most of the frozen tissues are not the type that are amenable to current cloning techniques. While the society is working with the San Diego Zoo to freeze some clonable cells, he too said that cloning is not the way to fight extinctions.

"The notion we can maintain frozen representatives and then reconstitute these animals in the future as a conservation technique — it just doesn't make sense," he said.