The present invention is a method of milling materials to form a fine powder with a median particle size below 10 micrometer which is suitable for inhalation and which has substantially no amorphous content generated during milling. The method is particularly suitable for milling materials which are soft. The method comprises milling the material in a fluid energy mill at reduced temperature using helium, or helium mixed with another gas, as milling fluid. Temperatures of -30 DEG C or less are used.
