Part Two, picks up the story in the late 19th century, when researchers plunged cold science to new lows as they succeeded in reaching the forbidding realm at which oxygen and then nitrogen liquefy. The master of this technology was Scottish chemist James Dewar, who pursued the holy grail of the field—liquefying hydrogen at minus 253 C, just 20 degrees above absolute zero. When he succeeded, he faced the unexpected and even more daunting challenge of liquefying the newly discovered gas helium at a mere 5 degrees above absolute zero. However, he had a talented competitor—Dutch physicist Heike Onnes—and the ensuing race to the bottom of the temperature scale was as zealous as the contemporaneous race to the Earth's poles.

The end of the 20th century produced another low-temperature contest. No one had ever seen an exotic form of matter called a Bose-Einstein condensate, which only forms at temperatures vanishingly close to absolute zero. But new techniques developed in the 1990s by Daniel Kleppner at the Massachusetts Institute of Technology set the stage for a race to create this truly bizarre substance—and with it win the latest heat in the quest for cold.

Source: http://www.pbs.org/wgbh/nova/zero/about.html

Part1: http://www.videosift.com/video/Absolute-Zero-The-Conquest-of-Cold-Part-1-of-2