The purity is one of the essential factors of the materials for preparing well controlled materials and devices, because the existence of ppm or sub-ppm level impurities leads to a significant and sometimes critical influence on the material properties and devise performance. Since the development of high technology depends strongly on the availability of high purity metals required for fabricating a new functional device, and furthermore, the purity of commercial pure materials for exploratory material researches is insufficient, the purification process that meets any requirements should be developed. In this article, based on our experience, we will describe how to construct the purification process, purification methods, and the purification of iron as an example. (C) 2011 Elsevier B. V. All rights reserved.