What is cryogenic engineering?

The question "Where is the final frontier of human?" gives a direct answer "SPACE". Space is so wide that there are lots of phenomena that exist beyond the limitation of our imagination. To represent the space in terms of temperature, in other words, for the question "What is the temperature of space?"-if we consider the black body radiation of deep space-we can answer "It is about 3K". Historically, the study of the phenomena in this low temperature world is called 'cryogenics'. 'Cryogenics' is originated from the Greek word "CRYO", which means 'cold', and the word "GEN", which means 'generate' in English. Nowadays cryogenics includes all phenomena occurring below 120 K, much lower temperature than that of typical refrigeration. There is an simple reason for treating cryogenics as a special field even though it is different from other fields in terms of just temperature. The physical properties of materials at very low temperature differ so dramatically from those commonly encountered that the engineer cannot rely on his ordinary experience. Cryogenic engineering is a technology that treats unusual phenomena at low temperature, covering not only physics but also chemistry, biology, mechanics, etc.