资料题：According to this passage, freezing is（　）。

Since the beginning of history, man has been fascinated by the idea of living forever, of winning the fight against death and disease.So far, this has only remained a dream, though a very powerful one.Many people have wondered whether it would be possible to find a way to preserve human bodies, and what would be the best way to preserve human bodies.It has long been known that meat or fruit can be kept fresh for long periods by freezing; in ancient China, for example, food was stored with ice to keep it fresh.This method could also be useful for preserving humans, and in fact many people have explored this possibility.However, most living beings that exist under warm conditions die when frozen.This is because of the harmful effects of freezing ice crystals, which are not only larger than the volume of the water originally in the cells, but also form sharp cutting shapes that ham the cells.In the 1940's, Dr B.J.Luyet and a group of scientists in England were working on the problem of freezing cells without damaging them.Since the harm caused by ice crystals was the main cause of the damage, Luyet suggested removing some or all of the water from the cells before freezing them.Using living cells from chickens, Luyet and his helpers discovered that they could partly dry the chicken cells, using a mixture of the white part of an e and glycerin (甘油), a clear,thick liquid made chiefly from fats and oils.Some success was obtained.The chicken cells were dried, frozen for a period of time, and then carefully unfrozen.Almost all the cells recovered when they reached normal temperatures.Since then, the cooling of whole animals to a temperature very much below freezing point for later unfreezing has become more of a possibility, and the glycerin method would probably beused to accomplish this.When this can be done completely successfully, science will have moved much closer to its aim of freezing and storing incurable patients until the day when they can be cured.