Abstract
Low temperature physicists are making a constant effort to extend the temperature range necessitated in the experimental researches closer and closer toward the absolute zero. These extentions of the temperature range toward the ultralow temperature always accompanied with the new and fundamentally important discoveries. Three methods for cooling to the ultralow temperature region are the 3He/4He dilution refrigeration, Pomeranchuk cooling and adiabatic nuclear demagnetization. The experimental investigations lie in this important unexplored teritory are hopeful and interesting.
