This reference overviews important developments in separation science since 1900, and covers recent advances and current techniques. Many contributors offer personal perspectives on their work and the work of colleagues in the field. Some topics examined include the development of chromatography, thin-layer chromatography, the evolution of capillary column gas chromatography, and a general theory of gradient elution. Other subjects discussed include gel permeation chromatography, field flow fractionation, solid phase microextraction, and a history of the use and measurement of affinity interactions in electrophoresis. Issaq is a scientist in the Analytical Chemistry Laboratory and manager of the Separation Technology Group at SAIC Frederick, NCI-Frederick Cancer Research and Development Center.