Our mastery of cold is something we take for granted, whether it s air conditioning and frozen food or the liquefied gases and superconductivity at the heart of cutting-edge technology. But what is cold? How do you achieve it, and how cold can it get? This two-part NOVA special brings the history of this frosty fascination to life with brilliant dramatic recreations of high moments in low-temperature research and the quest for ever-lower notches on the thermometer.The first hour, The Conquest of Cold, opens in the 1600s when the nature of cold and heat was a complete mystery. Were they different aspects of the same phenomenon? The experiments that settled these questions helped stoke the Industrial Revolution.